Absolute handedness control of oligoamide double helices by chiral oxazolylaniline induction

Ling Yang a, Chunmiao Ma a, Brice Kauffmann b, Dongyao Li a and Quan Gan *a
aHubei Key Laboratory of Bioinorganic Chemistry & Materia Medica, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China. E-mail: ganquan@hust.edu.cn
bUniversité de Bordeaux, CNRS, INSERM, IECB-UMS3033-US001, Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France

Received 21st July 2020 , Accepted 13th August 2020

First published on 14th August 2020


Aromatic oligoamide double helices bearing a chiral oxazolylaniline moiety at the C-terminus were synthesized and their helix handedness was completely controlled (de > 99%). The absolute helix sense and the de values were evaluated by using 1H NMR, X-ray crystallography, and circular dichroism (CD). Using crystal structure analysis, the high efficiency of helix handedness induction was attributed to the close location of the asymmetric carbon center to the helix orbits via intramolecular hydrogen bonding. The CD experiments also showed that there is no loss of chiral induction either in the interconversion of single and double helices or by elongation of the sequences.


Introduction

Stable helical molecular structures are ubiquitous in both biological and synthetic polymers.1 One of the intriguing features of these molecules is their inherent handedness (screw-sense) arising from their helical structures. In biomolecules, the bias of one handedness (P- or M-helicity) stems from the chirality of the monomers. For instance, B-DNA built from D-deoxyribose typically possesses P-helicity. In comparison, the synthetic oligomers, termed foldamers,2 might favour one handedness of the helix even though they are constructed from non-chiral building blocks, leading to potential applications in chiral sensing, chiral information transfer, and asymmetric catalysis.3 The screw sense bias might either come from a chiral inducer appended at the terminus of the sequence4 or from complexation with chiral guests in the cavity.5 In all these cases, the absolute handedness control has been achieved mostly for single sequences,6 whereas obtaining enantiomerically pure multiple helices made of non-chiral subunits is scarcely reported and challenging,7 albeit higher order of aggregation being utilized to increase the complexity and function of biomacromolecules. One may imagine that the full control of handedness could be obtained by chiral amplification8via cooperative communication among the multiple sequences, that is, by the classical sergeants and soldiers effect.9 However, the chiral transfer and enhancement to the absolute extent by this method is hard to predict.

Previous studies have shown that aromatic oligoamide foldamers could self-organize into helical structures upon forming intramolecular hydrogen bonds.10 Regarding their helicity, a stereogenic center such as a chiral phenethyl amino group at the C-terminus can induce bias favoring the one handedness of one sequence over another.4e–h More recently, Jiang unravelled the absolute handedness control of a single helical strand by introducing a chiral oxazolylaniline moiety.11 The full screw sense induction was ascribed to the stable three-center hydrogen bonding between the chiral oxazolylaniline moiety and 8-amino-2-quinolinecarboxylic acid of the helical scaffold. On the other hand, early research showed that the fluoroquinoline-based oligoamides could dimerize into stable antiparallel duplexes via the spring extension mechanism,12 in which the capability of helical chirality induction was preserved during the hybridization process.4f Following these, we proposed that an oligoamide double helix might adopt a complete chiral control by ligating the sequence with the same chiral oxazolylaniline moiety.

For this purpose, sequences 1–3 consisting of two kinds of units (Q: 8-amino-2-quinolinecarboxylic acid and Qf: 7-amino-8-fluoro-2-quinolinecarboxylic acid), and chiral oxazolylaniline inducers were designed and synthesized (Scheme 1). Based on early studies,12,13 the segments of the Qf unit of the two strands were supposed to dimerize with each other, whereas the segments made of the Q unit formed only single helical structures. Therefore, the heteromeric sequences 1–3 were expected to form antiparallel double helices, extruding the chiral promoters to the termini (Fig. 1). The elongation of the Qf units from the tetramer to the hexamer and to the octamer in the sequences was designed for the purpose of increasing the hybridization ability of the duplexes.


image file: d0ob01503b-s1.tif
Scheme 1 Synthesis of the chiral aromatic oligoamide foldamers 1–3. Reaction conditions: i. (a) 1-Chloro-N,N,2-trimethyl-1-propenylamine, CH2Cl2, room temp., 2 h; (b) iPr2EtN, room temp., 12 h; ii. TFA, CH2Cl2, room temp., 2 h; iii. iPr2EtN, room temp., 12 h.

image file: d0ob01503b-f1.tif
Fig. 1 Schematic representation of the hybridization of chiral single strands to an antiparallel double helix.

Results and discussion

The oligomers 1–3 were synthesized smoothly by successive acid chloride–amine condensation reactions (Scheme 1). Starting with the quinoline dimer acid 4, the chiral Q2 dimer 6 can be obtained by coupling it with the R- or S-oxazolylaniline compound 5. Afterward, the Boc group of 6 was removed with TFA to yield the chiral Q2 dimer amine 7, which was subsequently coupled with the acid chloride of Qf4 to generate oligomer 1. Oligomers 2 and 3 could also be obtained by coupling the corresponding acid chloride of Qf6/Qf8 to 7, respectively. The sequences were purified by column chromatography and characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry.

The elucidation of the double helical structures of 1–3 with chirality control has been initially performed using NMR experiments. Each foldamer exhibits different kinetic and thermodynamic hybridization properties depending on the length of the sequence. The 1H NMR spectra of 1 in CDCl3 shows a single set of slightly broad signals (Fig. 2a). Concentration-dependent NMR spectra suggest that 1 forms weak and labile aggregates in rapid exchange on the NMR time scale (Fig. S2). All the aromatic proton signals were shifted down-field with the increase in concentration. Such chemical-shift variations are a typical signature of ring-current effects arising from the intermolecular π–π stacking. The dimerization constant Kd was calculated to be 1.9 × 102 L mol−1 by fitting it with a simple dimerization isotherm according to the concentration-dependent NMR chemical-shift values at 296 K.14


image file: d0ob01503b-f2.tif
Fig. 2 Part of the 400 MHz 1H NMR spectra of a solution of 2 × 10−3 M of (a) 1, (b) 2, and (c) 3 in CDCl3. Amide proton signals of the single and double helices are marked with circles and diamonds, respectively, in b.

In comparison, the longer sequences 2 and 3 show slower kinetics and stronger affinity on hybridization. The 1H NMR spectra of 2 in CDCl3 displayed two sets of sharp signals with different integral intensity ratios that varied with changing concentration (Fig. S3). For instance, dilution, an efficient approach to dissociate aggregation of helices,10c increased the proportion of the minor set of signals. We thus attributed the minor species to the single helical structure of 2 and the major species to the double helix and inferred that they were in slow exchange on the NMR time scale. The relative chemical shifts of these two species support our speculation, as the signals of the double helix typically emerge at a higher field due to the shielding of the increased aromatic π–π stacking. The DOSY experiment (Fig. S6) further verified the assignment, the diffusion coefficients of the single and double helices were found to be 6.22 × 10−10 and 5.01 × 10−10 m2 s−1 (with hydrodynamic radii of 0.62 and 0.77 nm), respectively. In the case of 3, its 1H NMR spectra showed signals of the double helix considerably upfield compared with those of the double helix of 2 (Fig. 2b and c), while another set of signals with low intensities assigned to the single helix could only be observed at extreme concentrations (0.5 mM) at a lower field (Fig. S4). The integral proportion of these two species allowed us to estimate the dimerization constant Kd of 2 and 3 at 296 K in CDCl3 to be 2.2 × 104 L mol−1 and 4.0 × 105 L mol−1, respectively. All these results reflect the high propensity of the sequences to hybridize into double helix as well as the slowdown of the dimerization kinetics with the sequence elongated. The mass experiments also supported this behavior (Fig. 3). For example, both single and double helices of 1 were detected at m/z = 1885.7 as 1+ and 2+ charged species, respectively, with more proportion of single helix with reference to the calculated data. In contrast, 2 showed less proportion of the single helical species, and 3 showed only double helical species.


image file: d0ob01503b-f3.tif
Fig. 3 Electrospray ionization mass spectra of a solution of 20 μM of (a) 1, (b) 2, and (c) 3 in chloroform. The calculated data for single and double helices were superimposed and colored blue and red, respectively.

When a foldamer sequence is long enough to undergo slow interconversion on the NMR time scale, both the diastereomeric M- and P-helices bearing a chiral group should in principle be observed by 1H NMR if absolute handedness control were not achieved. Although two sets of sharp signals were observed for the longer sequences 2 and 3, they were proven to be single and double helical species and were in slow exchange on the NMR time scale. These results thus indicate that the chiral inductions are quantitative for both single and double helices of the sequences, and the diastereomeric excess (de) is >99%.

To examine the absolute helical sense of the antiparallel double structure, single-crystal X-ray structural analysis was carried out. The fine crystals of the chiral octamer S-2 suitable for analysis by X-ray diffraction were obtained by diffusing hexane into a chloroform solution of S-2. The crystal structure (Fig. 4) unambiguously validates the antiparallel double helical pattern, in which the Qf6 segments of two strands are intertwined with each other and the Q2 segments with the chiral inducers extruded to the helical ends. The structure analysis result also provides an attribution of the chiral matching: the P helicity of the foldamer is induced by the asymmetric carbon (S) of the chiral promoter. This matching relationship follows the same rule as observed in other chiral aromatic foldamers, where helicity is induced from the C-terminal of the sequence.4,11 The position of the proton on the asymmetric carbon points towards the helix, as a result, the terminal phenyl group points away from the helix, probably due to the requirement of minimization of steric hindrance. As expected, a stable three-center hydrogen bond network is formed between the terminal amide proton with both adjacent quinoline and oxazoline nitrogens in each strand, in agreement with the NMR data that the proton signal appears at low field (12.4 ppm). This driving force allows the asymmetric carbon to locate closely along the helix orbits, which was attributed to the quantitative handedness induction.


image file: d0ob01503b-f4.tif
Fig. 4 (a) The side view of the crystal structures of octamer S-2, and (b) the top view of the oxazolylaniline group showing its three-center hydrogen bonding network. Chloroform solvent molecules and isobutyl side chains have been omitted for clarity.

The helical sense of the sequences was further investigated by circular dichroism (CD) spectroscopy. The CD spectra of sequences with the S/R enantiomer of the inducer show perfect mirror bands in the absorption region of the quinoline rings between 250 nm and 450 nm, respectively (Fig. 5a). The positive CD Cotton effects correspond to the induction of P-helicity by S-oxazolylaniline as observed in the crystal structure, while M-helicity is induced by R-oxazolylaniline.4,11 Upon comparing these chiral foldamers, the CD absorption intensities increased linearly with the growth of the sequence length, suggesting that each fluoroquinoline monomer contributed the same intensity, and more importantly, there is no loss of chiral induction of helix sense with the elongation of the sequence. In addition, the CD absorption intensities were also found to increase linearly with the increase in concentration, as shown in Fig. 5b for S-2. In view of the fact that the proportion of single and double helices alters with the variation of concentration, this linear increase in trend indicates that chirality induction is invariable in the interconversion of single and double helices. Moreover, the temperature-variation CD experiments show only slight changes of the spectra with variation of temperature (Fig. S9–11). All these results are in agreement with the fact that the handedness is fully controlled for both single and double helices.


image file: d0ob01503b-f5.tif
Fig. 5 (a) Main figure, circular dichroism spectra of S/R isomers of 1–3 (4 × 10−5 M) in chloroform. Inset, a plot of the intensities of each isomer at 336 nm. (b) Main figure, circular dichroism spectra of S-2 at various concentrations in chloroform. Inset, a plot of the intensities at 336 nm versus concentration.

Conclusions

We have validated a strategy to construct artificial double helices with absolute handedness control. The chirality induction arose from a ligation of the chiral oxazolylaniline moiety at the terminus, while the fluoroquinoline segments allowed the sequences to dimerize into antiparallel double helices with handedness preservation. Taking account of the helix cavity, the absolute control of helicity of double helices would provide chances to develop chiral materials with specific functions, such as chiral sensing and supramolecular asymmetric catalysis.

Experimental

General information and methods

All chemicals and solvents were purchased from commercial suppliers and were used without further purification unless otherwise specified. Dichloromethane (DCM) was distilled over CaH2 prior to use. Column chromatography was carried out on Merck GEDURAN Si60 (40–63 μm). NMR spectra were recorded on Bruker AVANCE 400 MHz and 600 MHz spectrometers. Chemical shifts were calibrated using CDCl3 (7.26 ppm for 1H NMR, 77.16 ppm for 13C NMR). High-resolution electrospray ionization mass spectrometry (ESI-MS) was performed on a micro TOF II instrument featuring a Z spray source with electrospray ionization and modular LockSpray interface. CD spectra were recorded on a ChirascanTM circular dichroism spectrometer (Applied Photophysics Ltd, Surrey, United Kingdom).

General procedures for S-6 and R-6

The dimer acid 415 (200 mg, 0.3 mmol, 1.0 equiv.) was suspended in anhydrous DCM (5 mL) under argon. 1-Chloro-N,N,2-trimethylpropenylamine (79 μL, 0.6 mmol, 2.0 equiv.) was added carefully to the mixture. The reaction slowly turned to a yellow homogeneous solution over 2 h. The solution was concentrated in vacuo to give the acid chloride as a yellow solid, which was pumped dry for 2 h. S/R-516 (71 mg, 0.3 mmol, 1.0 equiv.) and DIEA (104 μL, 0.6 mmol, 2.0 equiv.) were dissolved in anhydrous DCM (5 mL) under argon with stirring. The above acid chloride was dissolved in anhydrous DCM (5 mL), and then added into amine liquor immediately. After stirring overnight, TLC analysis indicated completion of the reaction. The solution was concentrated under reduced pressure. The resultant crude material was purified by column chromatography to give compounds S- or R-6.
Compound S-6. Pale yellow solid (202 mg, 82% yield, purified by silica gel chromatography using hexane/EA 15[thin space (1/6-em)]:[thin space (1/6-em)]1–3[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 13.81 (s, 1H), 12.17 (s, 1H), 9.16 (d, J = 8.4 Hz, 1H), 8.93 (d, J = 7.1 Hz, 1H), 8.73 (s, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.98 (d, J = 7.7 Hz, 1H), 7.89 (d, J = 8.3 Hz, 1H), 7.78 (s, 1H), 7.74 (s, 1H), 7.70 (d, J = 7.8 Hz, 1H), 7.65–7.51 (m, 3H), 7.17 (t, J = 7.5 Hz, 1H), 6.96–6.84 (m, 3H), 6.70 (d, J = 6.7 Hz, 2H), 4.17 (dt, J = 10.3, 7.8 Hz, 3H), 4.11–4.03 (m, 1H), 3.55 (dt, J = 16.8, 7.6 Hz, 2H), 3.17–3.07 (m, 1H), 2.33 (ddd, J = 23.3, 13.4, 6.7 Hz, 2H), 1.33 (s, 9H), 1.17 (dd, J = 10.5, 6.7 Hz, 12H). 13C{1H} NMR (100 MHz, CDCl3): δ 164.7, 163.8, 163.8, 163.4, 163.0, 152.6, 151.5, 150.4, 141.4, 139.7, 138.9, 137.8, 135.6, 134.7, 132.7, 129.5, 128.4, 128.4, 127.7, 127.4, 126.0, 123.1, 122.3, 122.1, 120.6, 117.4, 117.0, 116.3, 114.5, 114.4, 99.8, 98.8, 80.7, 76.9, 75.6, 75.4, 72.5, 69.4, 28.4, 28.2, 19.4, 19.4. Mp: 137–139 °C. HRMS (ESI) calculated for C48H51N6O7 [M + H]+: 823.3819, found 823.3815.
Compound R-6. Pale yellow solid (197 mg, 80% yield, purified by silica gel chromatography using hexane/EA 15[thin space (1/6-em)]:[thin space (1/6-em)]1–3[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 13.81 (s, 1H), 12.17 (s, 1H), 9.16 (d, J = 8.4 Hz, 1H), 8.93 (d, J = 7.5 Hz, 1H), 8.73 (s, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 8.2 Hz, 1H), 7.78 (s, 1H), 7.74 (s, 1H), 7.70 (d, J = 7.0 Hz, 1H), 7.64–7.51 (m, 3H), 7.17 (t, J = 7.5 Hz, 1H), 6.96–6.85 (m, 3H), 6.70 (d, J = 6.8 Hz, 2H), 4.22–4.03 (m, 4H), 3.55 (dt, J = 16.8, 7.6 Hz, 2H), 3.16–3.07 (m, 1H), 2.33 (ddd, J = 23.2, 13.4, 6.7 Hz, 2H), 1.33 (s, 9H), 1.17 (dd, J = 10.5, 6.8 Hz, 12H). 13C{1H} NMR (100 MHz, CDCl3): δ 164.7, 163.8, 163.8, 163.4, 163.0, 152.6, 151.5, 150.4, 141.4, 139.7, 138.9, 137.8, 135.6, 134.7, 132.7, 129.5, 128.4, 128.4, 127.7, 127.4, 126.0, 123.1, 122.3, 122.1, 120.6, 117.4, 117.0, 116.3, 114.5, 114.4, 99.8, 98.8, 80.7, 76.9, 75.6, 75.4, 72.5, 69.4, 28.4, 28.2, 19.4, 19.4. Mp: 137–139 °C. HRMS (ESI) calculated for C48H51N6O7 [M + H]+: 823.3819, found 823.3832.

General procedure for chiral oligomers 1–3

S- or R-6 (123 mg, 0.15 mmol) was dissolved in DCM (5 mL) and excess TFA (2.5 mL) was added into the solution. The mixture was stirred at room temperature for 2 h. The solvent was evaporated and the residue was dissolved in DCM (20 mL), washed with saturated NaHCO3, dried over Na2SO4 and then evaporated to give chiral dimer amine 7 as a yellow solid. It was dried in vacuo and used without further purification. The obtained chiral dimer amine (108 mg, 0.15 mmol, 1.0 equiv.) and DIEA (52 μL, 0.30 mmol, 2.0 equiv.) were dissolved in anhydrous dichloromethane (5 mL) under argon with stirring. The corresponding fluoroquinoline acid chloride (8, 9 or 10)12 (0.17 mmol, 1.1 equiv.) was dissolved in anhydrous DCM (5 mL), and then added into the amine liquor immediately. After stirring overnight, TLC analysis indicated completion of the reaction. The solution was concentrated under reduced pressure. The resultant crude material was purified by column chromatography to give the chiral oligomers 1–3.
Compound S-1. Yellow solid (207 mg, 74% yield, purified by silica gel chromatography using DCM/EA 100[thin space (1/6-em)]:[thin space (1/6-em)]1–20[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 12.62 (s, 1H), 12.25 (s, 1H), 11.64 (s, 1H), 10.86 (s, 1H), 10.21 (s, 1H), 9.40 (s, 1H), 9.09 (d, J = 7.4 Hz, 1H), 8.80 (s, 1H), 8.62 (s, 1H), 8.22 (s, 1H), 8.17–8.00 (m, 2H), 7.95 (d, J = 8.2 Hz, 1H), 7.72 (d, J = 8.6 Hz, 1H), 7.64 (d, J = 9.1 Hz, 1H), 7.57 (d, J = 8.9 Hz, 1H), 7.45 (d, J = 7.3 Hz, 2H), 7.39 (s, 1H), 7.34–7.27 (m, 2H), 7.18 (dd, J = 17.1, 8.5 Hz, 2H), 7.05–6.93 (m, 3H), 6.90 (d, J = 6.3 Hz, 2H), 6.70 (t, J = 7.9 Hz, 1H), 6.58 (dt, J = 14.6, 7.1 Hz, 3H), 6.39 (d, J = 7.9 Hz, 1H), 6.24 (d, J = 7.4 Hz, 2H), 4.08 (ddd, J = 26.0, 14.4, 7.8 Hz, 4H), 3.99–3.85 (m, 3H), 3.71 (dd, J = 19.1, 11.5 Hz, 2H), 3.43 (t, J = 7.8 Hz, 1H), 3.13 (dd, J = 14.8, 7.9 Hz, 2H), 2.97–2.88 (m, 1H), 2.56–2.17 (m, 6H), 1.91 (dt, J = 13.0, 6.6 Hz, 1H), 1.68 (d, J = 5.6 Hz, 1H), 1.37 (dd, J = 6.5, 3.6 Hz, 6H), 1.31–1.17 (m, 18H), 1.10 (s, 9H), 0.92 (d, J = 6.7 Hz, 3H), 0.85–72 (m, 9H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.7, 162.6, 162.4, 162.3, 162.1, 162.0, 161.9, 161.6, 161.5, 161.0, 152.2, 151.1, 151.0, 150.1, 150.0, 149.9, 149.3, 147.3, 147.0, 146.4, 144.7, 144.4, 143.9, 143.8, 141.7, 139.3, 138.7, 138.0, 137.2, 137.1, 136.8, 136.7, 136.6, 136.2, 136.1, 135.3, 134.7, 131.3, 129.6, 128.1, 127.7, 127.6, 127.4, 127.0, 126.9, 126.8, 126.6, 125.6, 122.5, 121.3, 121.3, 120.2, 120.1, 119.4, 119.3, 119.2, 118.7, 118.7, 118.5, 117.9, 117.8, 116.9, 116.6, 115.2, 114.7, 113.9, 98.7, 98.0, 97.6, 97.1, 97.0, 96.9, 80.5, 76.9, 75.4, 75.4, 75.1, 75.0, 74.5, 74.3, 71.8, 68.8, 28.6, 28.4, 28.4, 28.1, 27.9, 27.9, 19.7, 19.7, 19.6, 19.6, 19.6, 19.4, 19.4, 19.3, 19.2, 19.2, 18.9. Mp: 241–244 °C. HRMS (ESI) calculated for C104H102F4N14O15Na [M + Na]+: 1885.7477, found 1885.7467.
Compound R-1. Yellow solid (201 mg, 72% yield, purified by silica gel chromatography using DCM/EA 100[thin space (1/6-em)]:[thin space (1/6-em)]1–20[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 12.63 (s, 1H), 12.26 (s, 1H), 11.65 (s, 1H), 10.87 (s, 1H), 10.23 (s, 1H), 9.42 (s, 1H), 9.09 (d, J = 7.5 Hz, 1H), 8.81 (s, 1H), 8.64 (s, 1H), 8.24 (s, 1H), 8.16–8.03 (m, 2H), 7.96 (d, J = 8.2 Hz, 1H), 7.75 (s, 1H), 7.68–7.55 (m, 2H), 7.48 (t, J = 13.7 Hz, 2H), 7.40 (s, 1H), 7.30 (d, J = 14.6 Hz, 2H), 7.23–7.13 (m, 2H), 7.00 (t, J = 7.0 Hz, 3H), 6.90 (s, 2H), 6.80 (s, 1H), 6.70 (t, J = 7.7 Hz, 1H), 6.59 (dt, J = 14.6, 7.0 Hz, 3H), 6.41 (d, J = 7.1 Hz, 1H), 6.24 (d, J = 7.2 Hz, 2H), 4.09 (ddd, J = 23.0, 13.7, 7.2 Hz, 4H), 3.99–3.85 (m, 3H), 3.77 (s, 1H), 3.73–3.64 (m, 1H), 3.44 (t, J = 7.6 Hz, 1H), 3.19–3.05 (m, 2H), 2.99–2.88 (m, 1H), 2.49–2.25 (m, 6H), 1.90 (dd, J = 12.8, 6.5 Hz, 1H), 1.69 (d, J = 5.6 Hz, 1H), 1.37 (dd, J = 6.5, 3.3 Hz, 6H), 1.31–1.16 (m, 18H), 1.10 (s, 9H), 0.92 (d, J = 6.7 Hz, 3H), 0.81 (dd, J = 15.4, 8.4 Hz, 9H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.7, 162.6, 162.3, 162.1, 162.0, 161.9, 161.6, 161.5, 161.0, 152.2, 151.1, 151.1, 150.1, 150.0, 149.9, 149.3, 147.3, 147.0, 146.4, 144.7, 144.4, 143.8, 141.7, 139.3, 138.7, 138.0, 137.2, 137.1, 136.8, 136.7, 136.2, 135.3, 134.7, 131.3, 129.6, 128.1, 127.7, 127.6, 127.4, 126.9, 126.8, 126.6, 125.6, 122.5, 121.3, 121.3, 120.2, 120.1, 119.4, 119.3, 119.2, 118.8, 118.7, 118.6, 117.9, 117.8, 116.9, 116.6, 115.2, 114.7, 113.9, 98.7, 98.0, 97.6, 97.1, 97.0, 96.9, 80.5, 76.9, 75.4, 75.4, 75.1, 75.0, 74.5, 74.3, 71.8, 68.8, 28.6, 28.4, 28.4, 28.2, 27.9, 27.9, 19.7, 19.7, 19.6, 19.6, 19.6, 19.4, 19.4, 19.3, 19.3, 19.2, 18.9. Mp: 241–244 °C. HRMS (ESI) calculated for C104H102F4N14O15Na [M + Na]+: 1885.7477, found 1885.7483.
Compound S-2. Yellow solid (232 mg, 65% yield, purified by silica gel chromatography using DCM/EA 80[thin space (1/6-em)]:[thin space (1/6-em)]1–10[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (600 MHz, CDCl3): δ 12.38 (s, 1H), 11.94 (d, J = 10.6 Hz, 1H), 11.48 (s, 1H), 10.86 (s, 1H), 10.21 (s, 1H), 9.95 (s, 1H), 9.67 (s, 1H), 9.33 (t, J = 15.9 Hz, 1H), 9.01 (d, J = 6.1 Hz, 1H), 8.69–8.56 (m, 1H), 8.44 (s, 1H), 8.07 (d, J = 7.0 Hz, 1H), 7.98 (s, 1H), 7.91 (t, J = 6.7 Hz, 1H), 7.80 (d, J = 7.9 Hz, 1H), 7.70–7.64 (m, 1H), 7.64–7.56 (m, 2H), 7.54 (d, J = 8.7 Hz, 1H), 7.38 (s, 1H), 7.34 (s, 1H), 7.31 (d, J = 6.9 Hz, 1H), 7.20 (d, J = 8.5 Hz, 1H), 7.13 (t, J = 10.4 Hz, 1H), 7.05 (t, J = 9.1 Hz, 2H), 6.99 (d, J = 8.5 Hz, 3H), 6.94 (s, 1H), 6.92 (s, 2H), 6.85 (dd, J = 12.6, 5.6 Hz, 1H), 6.82–6.78 (m, 2H), 6.71 (s, 1H), 6.65 (s, 1H), 6.54 (t, J = 7.1 Hz, 1H), 6.48 (t, J = 7.7 Hz, 2H), 6.43 (d, J = 7.8 Hz, 1H), 6.34 (d, J = 14.6 Hz, 1H), 6.12 (d, J = 8.0 Hz, 2H), 4.22 (t, J = 6.4 Hz, 1H), 4.17–4.11 (m, 2H), 4.08 (t, J = 7.0 Hz, 1H), 4.00 (t, J = 6.5 Hz, 1H), 3.93–3.87 (m, 2H), 3.84 (t, J = 6.4 Hz, 1H), 3.79 (dd, J = 12.3, 5.8 Hz, 1H), 3.73 (ddd, J = 23.0, 13.2, 6.6 Hz, 3H), 3.57 (t, J = 6.1 Hz, 1H), 3.37 (t, J = 7.0 Hz, 1H), 3.19 (t, J = 6.6 Hz, 1H), 3.00 (t, J = 6.0 Hz, 1H), 2.95 (t, J = 6.3 Hz, 1H), 2.77–2.71 (m, 1H), 2.47–2.35 (m, 2H), 2.34–2.20 (m, 4H), 2.05 (dt, J = 19.7, 9.9 Hz, 1H), 1.86–1.74 (m, 2H), 1.35–1.18 (m, 36H), 1.10 (s, 10H), 0.83 (t, J = 7.3 Hz, 3H), 0.80 (dd, J = 10.3, 6.8 Hz, 6H), 0.73 (t, J = 9.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.4, 162.4, 162.1, 161.9, 161.8, 161.7, 161.6, 161.3, 161.2, 161.1, 160.8, 160.7, 152.0, 150.3, 150.2, 149.9, 149.8, 149.7, 149.6, 149.1, 147.4, 146.6, 146.5, 146.2, 146.1, 145.7, 144.8, 144.0, 143.9, 143.6, 143.5, 143.1, 141.7, 139.3, 138.5, 137.6, 136.9, 136.8, 136.5, 136.5, 136.0, 135.8, 135.7, 135.3, 134.1, 131.1, 129.5, 128.0, 127.1, 127.0, 126.9, 126.8, 126.7, 126.6, 126.5, 126.4, 126.0, 125.9, 125.7, 125.6, 125.5, 125.4, 125.3, 122.3, 121.3, 120.7, 119.9, 119.7, 119.2, 119.1, 118.6, 118.4, 118.4, 118.2, 118.1, 117.8, 117.4, 117.1, 116.5, 116.2, 115.6, 115.1, 114.3, 113.7, 98.4, 97.9, 97.4, 97.3, 97.2, 97.0, 97.0, 96.9, 80.6, 76.9, 75.5, 75.3, 75.1, 74.9, 74.7, 74.3, 74.2, 71.6, 68.6, 28.5, 28.5, 28.4, 28.3, 28.0, 27.9, 27.8, 19.7, 19.6, 19.5, 19.5, 19.5, 19.4, 19.2, 19.2, 19.1, 19.0. HRMS (ESI) calculated for C264H258F12N36O38 [2M + 2H]2+: 2383.9580, found 2383.9583.
Compound R-2. Yellow solid (225 mg, 63% yield, purified by silica gel chromatography using DCM/EA 80[thin space (1/6-em)]:[thin space (1/6-em)]1–10[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 12.39 (s, 1H), 11.93 (s, 1H), 11.48 (s, 1H), 10.86 (s, 1H), 10.21 (s, 1H), 9.96 (s, 1H), 9.67 (s, 1H), 9.32 (d, J = 15.6 Hz, 1H), 9.01 (d, J = 7.4 Hz, 1H), 8.71–8.55 (m, 1H), 8.50–8.37 (m, 1H), 8.07 (d, J = 7.1 Hz, 1H), 7.98 (d, J = 6.9 Hz, 1H), 7.96–7.88 (m, 1H), 7.79 (d, J = 8.0 Hz, 1H), 7.66 (dd, J = 14.3, 7.9 Hz, 1H), 7.63–7.50 (m, 3H), 7.38 (s, 1H), 7.35–7.28 (m, 2H), 7.20 (d, J = 9.0 Hz, 1H), 7.15 (d, J = 9.1 Hz, 1H), 7.04 (dd, J = 13.6, 7.5 Hz, 3H), 7.01–6.96 (m, 2H), 6.93 (d, J = 7.5 Hz, 3H), 6.86 (t, J = 7.3 Hz, 1H), 6.80 (d, J = 4.9 Hz, 2H), 6.71 (t, J = 7.8 Hz, 1H), 6.63 (d, J = 13.9 Hz, 1H), 6.49 (ddd, J = 26.0, 16.5, 7.6 Hz, 4H), 6.34 (s, 1H), 6.12 (d, J = 7.4 Hz, 2H), 4.26–4.17 (m, 1H), 4.16–4.09 (m, 2H), 4.09–4.02 (m, 1H), 4.02–3.95 (m, 1H), 3.95–3.65 (m, 6H), 3.61–3.52 (m, 1H), 3.38 (dd, J = 16.8, 9.1 Hz, 1H), 3.19 (t, J = 7.4 Hz, 1H), 3.01 (t, J = 6.7 Hz, 1H), 2.97–2.90 (m, 1H), 2.78–2.68 (m, 1H), 2.42 (ddd, J = 19.3, 12.9, 6.6 Hz, 2H), 2.36–2.16 (m, 4H), 2.03 (dd, J = 18.5, 7.7 Hz, 2H), 1.79 (ddd, J = 20.3, 13.5, 6.8 Hz, 2H), 1.36–1.17 (m, 36H), 1.09 (s, 9H), 0.88 (t, J = 6.8 Hz, 3H), 0.85–0.78 (m, 6H), 0.74 (d, J = 6.7 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.4, 162.4, 162.1, 161.9, 161.8, 161.7, 161.6, 161.3, 161.2, 161.1, 160.8, 160.7, 152.0, 150.3, 150.2, 149.9, 149.8, 149.7, 149.6, 149.1, 147.4, 146.6, 146.2, 146.1, 145.7, 144.8, 144.0, 143.9, 143.6, 143.5, 143.1, 141.7, 139.3, 138.6, 137.6, 136.9, 136.8, 136.6, 136.5, 136.0, 135.8, 135.7, 135.6, 135.3, 134.1, 131.1, 129.5, 128.0, 127.1, 127.0, 126.9, 126.8, 126.7, 126.6, 126.5, 126.4, 126.0, 125.9, 125.7, 125.6, 125.5, 125.4, 125.3, 122.3, 121.3, 120.7, 119.9, 119.7, 119.2, 119.1, 118.6, 118.4, 118.4, 118.2, 118.1, 117.8, 117.4, 117.1, 116.5, 116.2, 115.6, 115.1, 114.3, 113.7, 98.4, 97.9, 97.3, 97.2, 97.1, 97.0, 96.9, 80.6, 76.9, 75.5, 75.3, 75.1, 74.9, 74.7, 74.3, 74.2, 71.6, 68.6, 28.5, 28.5, 28.4, 28.3, 28.0, 27.9, 27.8, 19.7, 19.6, 19.5, 19.5, 19.5, 19.4, 19.2, 19.2, 19.1, 19.0. HRMS (ESI) calculated for C264H258F12N36O38 [2M + 2H]2+: 2383.9580, found 2383.9588.
Compound S-3. Yellow solid (270 mg, 62% yield, purified by silica gel chromatography using DCM/EA 50[thin space (1/6-em)]:[thin space (1/6-em)]1–10[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (600 MHz, CDCl3): δ 12.33 (s, 1H), 11.85 (s, 1H), 11.36 (s, 1H), 10.89 (s, 1H), 10.62 (s, 1H), 10.37 (d, J = 3.5 Hz, 1H), 9.75 (d, J = 3.2 Hz, 1H), 9.61 (dd, J = 10.9, 3.5 Hz, 2H), 9.25 (d, J = 3.7 Hz, 1H), 9.12 (d, J = 6.8 Hz, 1H), 8.65–8.56 (m, 1H), 8.46–8.41 (m, 1H), 8.38 (d, J = 6.9 Hz, 1H), 8.28–8.22 (m, 1H), 8.19–8.12 (m, 1H), 8.07–8.01 (m, 1H), 8.01–7.95 (m, 1H), 7.75 (s, 1H), 7.71 (d, J = 7.7 Hz, 1H), 7.48 (d, J = 8.4 Hz, 1H), 7.44 (d, J = 9.4 Hz, 1H), 7.36 (d, J = 8.6 Hz, 1H), 7.30 (dd, J = 8.7, 7.5 Hz, 1H), 7.27 (d, J = 6.8 Hz, 4H), 7.17 (dd, J = 17.3, 8.1 Hz, 2H), 7.08 (dd, J = 15.7, 8.6 Hz, 3H), 7.01 (t, J = 7.0 Hz, 1H), 6.89 (s, 1H), 6.85 (t, J = 6.8 Hz, 1H), 6.75–6.64 (m, 4H), 6.63 (s, 1H), 6.53 (s, 1H), 6.47 (t, J = 7.2 Hz, 1H), 6.43–6.37 (m, 3H), 6.26 (dd, J = 15.6, 8.3 Hz, 3H), 6.15 (s, 1H), 6.05 (d, J = 7.9 Hz, 2H), 4.14 (dt, J = 12.0, 6.2 Hz, 2H), 4.06–3.97 (m, 3H), 3.95 (t, J = 5.3 Hz, 1H), 3.92–3.88 (m, 1H), 3.86 (t, J = 6.9 Hz, 1H), 3.80 (t, J = 6.0 Hz, 1H), 3.75 (t, J = 5.8 Hz, 1H), 3.70 (t, J = 6.7 Hz, 1H), 3.69–3.63 (m, 2H), 3.58–3.49 (m, 4H), 3.29 (t, J = 6.8 Hz, 1H), 3.09 (t, J = 6.3 Hz, 1H), 3.01–2.95 (m, 1H), 2.93 (t, J = 6.3 Hz, 1H), 2.60–2.53 (m, 1H), 2.36 (dt, J = 13.6, 6.6 Hz, 2H), 2.28–2.18 (m, 5H), 2.14 (dd, J = 13.0, 6.7 Hz, 1H), 2.03–1.96 (m, 1H), 1.76 (ddt, J = 26.4, 13.2, 6.8 Hz, 2H), 1.36–1.10 (m, 48H), 1.04 (s, 9H), 0.82–0.74 (m, 9H), 0.66 (d, J = 6.8 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.4, 162.4, 162.3, 162.1, 161.8, 161.8, 161.7, 161.6, 161.3, 161.3, 161.2, 161.0, 161.0, 160.9, 160.7, 160.6, 151.6, 150.6, 150.1, 150.1, 149.9, 149.6, 149.3, 149.2, 149.1, 149.1, 148.9, 147.3, 146.9, 146.7, 146.3, 146.2, 145.7, 145.6, 144.7, 144.3, 144.1, 143.7, 143.7, 143.2, 143.0, 141.6, 139.2, 138.5, 137.5, 136.8, 136.7, 136.5, 136.4, 136.3, 136.2, 136.1, 135.8, 135.7, 135.5, 135.4, 135.3, 135.3, 134.2, 131.1, 129.5, 127.9, 127.3, 126.6, 126.6, 126.5, 126.4, 126.3, 126.3, 126.1, 126.0, 125.4, 125.3, 125.2, 125.2, 122.3, 121.2, 120.6, 119.9, 119.8, 119.6, 119.5, 119.1, 118.8, 118.5, 118.4, 118.3, 118.1, 117.6, 117.4, 117.4, 117.0, 116.8, 116.8, 116.4, 116.0, 115.4, 115.4, 115.0, 114.8, 114.4, 113.6, 98.2, 97.8, 97.7, 97.6, 97.4, 97.2, 96.9, 96.6, 96.4, 95.8, 80.6, 75.4, 75.2, 75.2, 74.8, 74.7, 74.2, 71.5, 68.4, 28.6, 28.5, 28.4, 28.4, 28.2, 28.0, 27.8, 27.7, 19.9, 19.7, 19.6, 19.6, 19.5, 19.5, 19.4, 19.4, 19.3, 19.3, 19.3, 19.1, 19.1, 19.0, 18.9. HRMS (ESI) calculated for C320H310F16N44O46 [2M + 2H]2+: 2904.1502, found 2904.1512.
Compound R-3. Yellow solid (279 mg, 64% yield, purified by silica gel chromatography using DCM/EA 50[thin space (1/6-em)]:[thin space (1/6-em)]1–10[thin space (1/6-em)]:[thin space (1/6-em)]1). 1H NMR (400 MHz, CDCl3): δ 12.34 (s, 1H), 11.85 (s, 1H), 11.36 (s, 1H), 10.88 (s, 1H), 10.63 (s, 1H), 10.37 (s, 1H), 9.73 (s, 1H), 9.62 (d, J = 12.3 Hz, 2H), 9.25 (s, 1H), 9.13 (d, J = 7.2 Hz, 1H), 8.69–8.54 (m, 1H), 8.51–8.33 (m, 2H), 8.30–8.21 (m, 1H), 8.21–8.12 (m, 1H), 8.10–7.93 (m, 2H), 7.81–7.63 (m, 2H), 7.42 (dt, J = 45.4, 12.1 Hz, 3H), 7.33–7.27 (m, 4H), 7.18 (dd, J = 17.0, 8.6 Hz, 3H), 7.12–6.97 (m, 4H), 6.90–6.81 (m, 2H), 6.75–6.60 (m, 5H), 6.44 (ddd, J = 19.4, 12.9, 5.5 Hz, 5H), 6.26 (t, J = 8.9 Hz, 3H), 6.13 (s, 1H), 6.05 (d, J = 7.6 Hz, 2H), 4.19–4.07 (m, 2H), 4.07–3.96 (m, 3H), 3.96–3.82 (m, 3H), 3.73 (ddd, J = 24.0, 14.4, 7.6 Hz, 6H), 3.54 (d, J = 6.4 Hz, 5H), 3.28 (t, J = 7.4 Hz, 1H), 3.08 (t, J = 7.1 Hz, 1H), 2.98 (t, J = 6.5 Hz, 1H), 2.91 (s, 1H), 2.59–2.49 (m, 1H), 2.35 (td, J = 13.3, 6.7 Hz, 2H), 2.27–2.15 (m, 5H), 2.04–1.93 (m, 2H), 1.35–1.12 (m, 48H), 1.03 (s, 9H), 0.77 (t, J = 6.8 Hz, 9H), 0.65 (d, J = 6.6 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 162.4, 162.3, 162.2, 162.1, 161.8, 161.8, 161.7, 161.6, 161.3, 161.3, 161.2, 161.0, 160.9, 160.9, 160.7, 160.6, 151.6, 150.6, 150.1, 150.1, 149.9, 149.6, 149.3, 149.2, 149.1, 149.1, 148.9, 147.3, 146.9, 146.7, 146.2, 145.7, 145.6, 144.8, 144.3, 144.1, 143.7, 143.7, 143.2, 143.0, 141.6, 139.2, 138.5, 137.5, 136.8, 136.7, 136.5, 136.4, 136.3, 136.2, 136.1, 135.8, 135.7, 135.5, 135.4, 135.3, 134.2, 131.1, 129.5, 127.9, 127.3, 126.6, 126.6, 126.5, 126.4, 126.3, 126.1, 126.0, 125.4, 125.3, 125.2, 125.2, 122.3, 121.2, 120.6, 119.9, 119.8, 119.5, 119.1, 118.8, 118.5, 118.4, 118.3, 118.1, 117.6, 117.4, 117.4, 117.0, 116.8, 116.8, 116.4, 116.0, 115.4, 115.4, 115.0, 114.9, 114.4, 113.6, 98.2, 97.8, 97.7, 97.6, 97.4, 97.2, 96.9, 96.6, 96.4, 95.8, 80.6, 76.9, 75.4, 75.2, 75.2, 74.8, 74.7, 74.2, 28.6, 28.5, 28.4, 28.4, 28.2, 28.0, 27.8, 27.7, 19.9, 19.7, 19.6, 19.6, 19.5, 19.5, 19.4, 19.4, 19.3, 19.3, 19.3, 19.1, 19.1, 19.0, 19.0. HRMS (ESI) calculated for C320H310F16N44O46 [2M + 2H]2+: 2904.1502, found 2904.1510.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (21871101) and the Natural Science Foundation of Hubei Scientific Committee (2017CFA036 and 2019ACA125). We are grateful to the Analysis and Testing Center at Huazhong University of Science and Technology for their help with materials characterization.

Notes and references

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Footnote

Electronic supplementary information (ESI) available. CCDC 2009252. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/d0ob01503b

This journal is © The Royal Society of Chemistry 2020