View PDF VersionPrevious ArticleNext Article
 
DOI: 10.1039/C3RA46007J (Paper) RSC Adv., 2014, 4, 6239-6245

Synthesis and characterization of N-acyl-tetra-O-acyl glucosamine derivatives†

Chi-Hien Dang*a, Cong-Hao Nguyena, Thanh-Danh Nguyen*ab and Chan Imb
aDepartment of Pharmaceutical Chemistry, Institute of Chemical Technology, VAST, Vietnam. E-mail: dangchihien@gmail.com; Tel: +84 8 38238265
bDepartment of Chemistry, Konkuk University, Korea. E-mail: danh5463bd@yahoo.com; Tel: +82 2 4503415

Received 24th October 2013 , Accepted 17th December 2013

First published on 20th December 2013

Abstract

Novel 1,3,4,6-tetra-O-acyl-N-acyl-D-glucosamine derivatives were synthesized from glucosamine hydrochloride (GlcN·HCl) by the acylation with pyridine as a catalyst. A derivative of tetra-O-acetyl glucosamine contained ketoprofen, a non-steroidal anti-inflammatory drug (NSAID) with analgesic and antipyretic effects, was first synthesized. In analysis of the NMR spectra, the ratio of α:β-anomer showed that penta-acyl-D-glucosamine derivatives and N-acetylated glucosamines containing O-acyl groups have been only the α-anomer. Meanwhile, both the intermediates and the glucoconjugate compound of ketoprofen have only the β-anomer.

Introduction

Rheumatoid arthritis1–4 is a common disease in the elderly. Glucosamine is a precursor for glucosaminoglycans, which are major components of joint cartilage. The glucosamine supplement may influence the cartilage structure. Therefore, the glucosamine may be proposed to treat the arthritis and alleviate symptoms.5–8 In recent years, the drugs containing glucosamine derivatives9–11 have been widely used to treat and restore the damaged cartilage. Advantages of the drug containing glucosamine strictly treated the arthritis without causing side effects. The research of Poustie12 showed that the acyl derivatives of glucosamine on the amino group (–NH2) possessed stronger activity than glucosamine itself in the treatment of arthritis. In particular, N-butyryl-D-glucosamine was also the most active component. Moreover, Some tetra-O-acyl-N-acyl-D-glucosamine13,14 were important intermediates in the oligosaccharide synthesis. The acetate and the n-butyrate esters of glucosamine have demonstrated activity against cancer cells.15,16

NSAIDs17–19 have also been used in the treatment of rheumatoid arthritis. In this purpose, Numerous NSAIDs ester derivatives have been synthesized to reduce gastro intestinal side-effect. It was also known that glucoconjugates could be transported by cellular glucose transporters. Therefore, the glucoconjugates of NSAIDs were recently prepared with the objective of increasing the bioavailability of antioxidant and anti-inflammatory drugs such as, ibuprofen,20 aspirin, diclofenac and indomethacin.21,22 These findings indicated that the glucoconjugates of NSAIDs might lead to reduce ulcerogenic potency, increase bioavailability and possess coordinative effects on osteoarthritis.

Some acyl derivatives of this amino sugar with fatty acids have been previously reported in the literature.14,15,23 However, their NMR spectra data has not revealed whether or not influence of N- and O-substituted groups to the α:β-isomer ratio of these derivatives. Our initial research24 revealed that the short fatty acid groups have been giving the isomer ratio by the rules. In this paper, we describe the synthesis and NMR spectral data analysis of a series penta-acyl-D-glucosamine, 1,3,4,6-tetra-O-acyl-N-acyl-D-glucosamine derivatives and a novel glucoconjugate of ketoprofen, which is prepared from GlcN·HCl. In synthesis of the glucoconjugate compound, a series of the compounds containing O-acetyl groups was also prepared.

Results and discussion

Synthesis

The glucosamine derivatives containing both N-acyl groups and O-acyl groups were prepared via two ways. First, 1,3,4,6-tetra-O-acyl-N-acylglucosamine, which was generated in two steps from commercially available GlcN·HCl, was synthesized by N-acetylation reaction of GlcN·HCl carried out with the various acid anhydrides in sodium methoxide solution to give the compounds 1–4. Esterification of these compounds was then performed by treatment with acid anhydrides in the presence of pyridine as the method previously reported.24 In the second approach, the penta-O-acyl glucosamine derivatives 13–15 were directly prepared from GlcN·HCl and acetic anhydride, propionic anhydride or butyric anhydride by using pyridine as a catalyst (Scheme 1).
image file: c3ra46007j-s1.tif
Scheme 1 Synthesis of tetra-O-acyl-N-acyl-D-glucosamine derivatives from GlcN·HCl.

The synthesis of glucoconjugate of NSAIDs has been described by different methods using various acetylated glucosamine analogues as glycosyl donors.12,21 A synthesis of 18 from GlcN·HCl using esterification of NH2 of glucosamine by ketoprofen chloride12 and followed the acetylation of all four OH groups of sugar ring by acetic anhydride was attempted. However, in our experiment, ketoprofen chloride as a key intermediate obtained from ketoprofen and thionyl chloride were synthesized in a low yield. Alternatively, the use of 1,3,4,6-tetra-O-acetyl-β-D-glucosamine hydrochloride (17) as a glycosyl donor12,25 gave good yield as described in Scheme 2.


image file: c3ra46007j-s2.tif
Scheme 2 Synthesis of D-glucosamine derivatives from GlcN·HCl and ketoprofen.

Compound 16 was obtained from commercially available GlcN·HCl in a procedure that used p-anisaldehyde for protection of –NH2 group in 67.82% yield. Acetylation and removal of the p-methoxybenzylidene group with HCl in acetone were to give 17 in 91.3% yield. The ester 18 was obtained by esterifying ketoprofen with amine glycosyl compound 17 in the presence of DCC/DMF–Py–Et3N in 51.5% yield after purification by silica gel column chromatography.

NMR spectra

The structure of the synthesized N-acyl, tetra-O-acyl-N-acyl-D-glucosamine and glucoconjugate derivatives was confirmed by 1H and 13C NMR spectroscopy (see Table 1 and 3, respectively). Analysis of the NMR spectra of 7 and 9–12 showed that structure and size of N-acyl group affected the chemical shifts of α and β-anomer. Simultaneously, the α:β-anomer ratios of the acylated glucosamines, that were determined by comparison of proton coupling constants of the H-1 peaks in the 1H NMR spectra, depended on the length of the carbon chain of the acyl groups at C-1 and C-2 of glucosamine. However, the chemical shifts of the sugar ring protons or carbons of 16–18 were not affected by the substituted groups which had the source from p-anisaldehyde or ketoprofen.
Table 1 Chemical shifts (ppm) of the protons in the 1H NMR spectra of tetra-O-acyl-N-acyl-D-glucosamine derivativesa
  Sugar moiety N–H Acyl groups
H-1 H-2 H-3 H-4 H-5 H-6
H-6a H-6b N-acyl O-acyl
a NMR experimental conditions: 500 MHz, CDCl3.
5 6.19 (d, 3.5 Hz) 3.96 (m) 5.26–5.22 (m) 4.44 (ddd, 19.5, 10, 4 Hz) 4.07 (dd, 12.5, 2.5 Hz) 4.17 (dd, 12.5, 4.5 Hz) 5.56 (d, 9 Hz) N–COMe: 1.91 (3H, s) OCOPr: 2.20–2.42 (8H, m); 1.56–1.75 (8H, m); 0.80–1.00 (12H, m)
6 5.69 (d, 9 Hz) 4.31 (m) 5.1 (t, 9.5 Hz) 5.17 (t, 9.5 Hz) 3.82 (m) 4.12 (dd, 12.5, 2.5 Hz) 4.25 (dd, 12.5, 4.5 Hz) 5.84 (d, 9.5 Hz) N–COPr: 2.01 (2H, m); 1.57 (2H, dd, 15.75 Hz); 0.88 (3H, t, 7.5 Hz); O–COMe: 2.01–2.11 (12H, m)
7 α 6.21 (d, 3.5 Hz) 4.48 (ddd, 12.5, 9, 1.5 Hz) 5.21–5.5.29 (m) 4.01 (m) 4.07 (d, 11.5 Hz) 4.23 (dd, 12.5, 4.5 Hz) 5.72 (d, 8.5 Hz) N–COPr: 2.05 (2H, m); 1.54 (2H, m). 0.88 (3H, t, 2.5 Hz) O–COEt: 2.27–2.49 (8H, m); 1.07–1.22 (16H, m)
β 5.73 (d, 9 Hz) 4.33 (q, 10 Hz) 3.85 (m) 6.13 (d, 9.5 Hz)
8 6.19 (d, 3.5 Hz) 4.47 (ddd, 13, 9, 1.25 Hz) 5.24 (quint, 9 Hz) 3.98–4.01 (m) 4.07 (dd, 12.5, 2.5 Hz) 4.22 (dd, 12.5, 4.5 Hz) 5.53 (d, 8.5 Hz) N–COMe: 1.92 (3H, s) O–COEt: 2.25–2.48 (8H, m); 1.09–1.23 (12H, m)
9 α 6.18 (d, 3.5 Hz) 4.43 (ddd, 12.5, 9, 1.5 Hz) 5.22–5.18 (quint, 10 Hz) 3.95 (m) 4.06 (dd, 12.5, 2 Hz) 4.15 (dd, 12.5, 4.5 Hz) 5.52 (d, 9 Hz) NHCOEt: 2.06 (2H, m); 1.04–1.08 (3H, m) O–COPr: 2.15–2.25 (8H, m); 1.55–1.73 (8H, m); 0.89–0.99 (12H, m)
β 5.67 (d, 8.5 Hz) 4.3 (m) 5.13 (quint, 10 Hz) 3.78 (m) 4.13 (dd, 12.5, 2.5 Hz) 4.19 (dd, 12.5, 4.5 Hz) 5.57 (d, 9 Hz)
10 α 6.29 (d, 3.5 Hz) 4.70 (dd, 11.5, 3.5 Hz) 4.35 (dd, 12.5.4 Hz) 6.54 (dd, 11, 2.5 Hz) 5.15 (dd, 10.5, 1 Hz) 4.13 (dd, 12, 2 Hz) 4.35 (dd, 12.5, 4 Hz) — N(CO)2C6H4: 7.83 (2H, m); 7.74 (2H, m) O–COMe: 1.87–2.12 (9H, s)
β 6.51 (d, 9 Hz) 4.45 (dd, 11.5, 9 Hz) 4.02 (m) 5.19 (dd, 10, 1 Hz) 5.87 (dd, 11.5, 1.5 Hz) 4.14 (dd, 12, 2.5 Hz) 4.3 (dd, 12.5; 4 Hz) —
11 α 6.31 (d, 3.5 Hz) 4.72 (dd, 11.5, 3.5 Hz) 4.31 (m) 6.54 (dd, 11.5; 2.5 Hz) 5.17 (t, 9.5 Hz) 4.12 (m) 4.31 (m) — N(CO)2C6H4: 7.83 (2H, m); 7.75 (2H, m) O–COEt: 2.04–2.41 (8H, m); 0.87–1.27 (12H, m)
β 6.52 (d, 9 Hz) 4.46 (dd, 10.5, 1.5 Hz) 4.06 (m) 5.24 (t, 9.75 Hz) 5.89 (dd, 10.5, 1.5 Hz) —
12 α 6.30 (d, 3.5 Hz) 4.72 (dd, 11.5, 3.5 Hz) 4.29 (m) 6.54 (dd, 11.5, 2.5 Hz) 5.17 (t, 9.5 Hz) 4.08 (m) 4.29 (m) — N(CO)2C6H4: 7.82 (2H, m); 7.71 (2H, m) O–COPr: 2.07–2.35 (8H, m); 1.24–1.62 (8H, m); 0.65–0.98 (12H, m)
β 6.52 (d, 9 Hz) 4.44 (dd, 12, 2 Hz) 3.8 (m) 5.22 (t, 9.5 Hz) 5.9 (dd, 10.5, 1.5 Hz) 4.08 (m) 4.29 (m) —
13 6.17 (d, 2.5 Hz) 4.48 (m) 5.14–5.27 (m) 4.0 (d, 9.5 Hz) 4.05 (d, 12.5 Hz) 4.23 (dd, 12, 3.5 Hz) 5.77 (m) N–COMe: 2.19 (3H, s) O–COMe: 1.93–2.11 (12H, s)
14 6.19 (d, 3.5 Hz) 4.47 (m) 5.24 (quint, 9.25 Hz) 3.99 (m) 4.07 (d, 7.5 Hz) 4.22 (dd, 12.5, 4.5 Hz) 5.55 (m) N–COEt: 2.44 (2H, q, 7 Hz); 1.21 (3H, t, 7.5 Hz); OCOEt: 2.09–2.4 (8H, m); 1.07–1.16 (12H, m)
15 6.21 (d, 3.5 Hz) 3.97 (m) 5.20–5.24 (m) 4.45 (ddd, 19, 10, 3.5 Hz) 4.07 (dd, 12.5, 2 Hz) 4.17 (dd, 2.5, 4.5 Hz) 5.54 (d, 9 Hz) N–COPr: 2.04 (2H, m); 1.54 (2H, m); 0.87 (3H, m); OCOPr: 2.2–2.41 (8H, m); 1.54–1.78 (8H, m); 1.02–0.87 (12H, m)
18 5.64 (d, 8.5 Hz) 3.74 (m) 5.07–5.18 (m) 4.26 (m) 4.07 (dd, 12.5, 2 Hz) 4.22 (dd, 12.5, 4 Hz) 6.08 (d, 9.5 Hz) 1.47 (3H, d, 7 Hz); 3.52 (1H, q, 7 Hz); 7, 4 (1H, dt, 7.5; 3 Hz); 7.48 (3H, m); 7.59 (2H, m); 7.69 (1H, s); 7.78 (2H, dd, 7; 3.5 Hz) 4 OAc: 1.82–2.06 (12H, s)

Physical characteristics and ratio of α- and β-isomer of the glucosamine derivatives were showed in Table 2. The α-anomer was preferred for N-acetylated glucosamine with different O-acyl groups such as acetyl, n-propionyl, n-butyryl or even indomethacinyl-substituent.22 With N-phthalated glucosamine, a mixture of the isomers was generated from which derivatives were substituted by shortly fatty groups on the O atom. In exception of the above cases, the β-anomer was preferred for the derivatives containing O-acetyl. The interesting results from Table 2 also showed that penta-acyl-D-glucosamine derivatives (13–15) gave more stable α-stereoisomer. In addition, N-acyl-D-glucosamine derivatives were obtained as a mixture of isomers in which the α-stereoisomer predominated.

Table 2 Ratio of α- and β-isomer and physical characteristics of compounds 1–18
N-Acyl groups (or N-substituent) O-Acyl groups (or O-substituent) Ratio of isomers Substances Mp (°C) [α]20D (solvent) Rf (EtOAc[thin space (1/6-em)]:[thin space (1/6-em)]PEa)
α β
a PE: petroleum ether; EtOAc: ethyl acetate.
CH3CO — Priority Lower 1 200–201 +65 (H2O) —
CH3CO 100% 0% 13 113–114 +86.5 (EtOH) 0.3 (2[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CO 100% 0% 8 155–156 +95.5 (EtOH) 0.5 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CH2CO 100% 0% 5 151–152 +80 (EtOH) 0.6 (3[thin space (1/6-em)]:[thin space (1/6-em)]2)
Indomethacin22 100% 0% — — — —
CH3CH2CO — Priority Lower 2 184–185 +36 (H2O) —
CH3CO23 0% 100% — — — —
CH3CH2CO 100% 0% 14 105–106 +81 (EtOH) 0.4 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CH2CO 83% 27% 9 108–110 +94 (EtOH) 0.5 (2[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CH2CO — Priority Lower 3 208–209 +33 (H2O) —
CH3CO 0% 100% 6 141–142 +33 (EtOH) 0.4 (2[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CO 59% 41% 7 Liquid +64 (EtOH) 0.4 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CH2CO 100% 0% 15 94–95 +65 (EtOH) 0.5 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
C6H4(CO)2 — 54% 46% 4 67–69 +25 (H2O) —
CH3CO 66% 34% 10 89–90 +66 (EtOH) 0.3 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CO 66% 34% 11 50–52 +117 (EtOH) 0.5 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
CH3CH2CH2CO 55% 45% 12 48–49 +110 (EtOH) 0.4 (2[thin space (1/6-em)]:[thin space (1/6-em)]1)
Anisaldehyde CH3CO 0% 100% 16 175–176 +98 (CHCl3) 0.4 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)
NH2·HCl CH3CO 0% 100% 17 220–222 +27 (H2O) -
Ketoprofen CH3CO 0% 100% 18 134–135 +7 (CHCl3). 0.5 (1[thin space (1/6-em)]:[thin space (1/6-em)]1)

Table 3 Chemical shifts (ppm) of the carbon atoms in the 13C NMR spectra of tetra-O-acyl-N-acyl-D-glucosamine derivativesa
  Sugar moiety Acyl groups
C-1 C-2 C-3 C-4 C-5 C-6 N-acyl O-acyl
a NMR experimental conditions: 125 MHz, CDCl3.
5 90.44 51.30 70.40 67.20 69.96 61.43 169.76 (C[double bond, length as m-dash]O) 172.44; 173.23; 171.24; 171.66 (C[double bond, length as m-dash]O); 36.02; 36.00; 35.86; 35.85 (–COCH2–); 18.40; 18.36; 18.30; 18.24 (CH2CH2–); 13.60; 13.56; 13.50; 13.50 (–CH3)
22.99 (CH3)
6 92.64 52.62 72.88 67.98 72.62 61.75 172.98 (C[double bond, length as m-dash]O) 171.17; 170.64; 169.48; 169.27 (C[double bond, length as m-dash]O); 20.81; 20.67; 20.62; 20.53 (–CH3)
38.56 (–COCH2)
19.00 (–CH2CH2)
13.49 (–CH3)
7 α 90.41 50.94 70.43 67.30 69.74 61.39 172.03 (C[double bond, length as m-dash]O) 175.05; 173.97; 172.83; 172.49 (C[double bond, length as m-dash]O); 27.33; 27.22; 27.18 (COCH2); 8.91; 8.82; 8.78 (CH3)
38.19 (COCH2)
18.79 (–CH2CH2)
13.36 (–CH3)
β 92.51 52.48 72.42 67.68 72.85 61.50 172.91 (C[double bond, length as m-dash]O) 174.48; 172.87; 172.63 (C[double bond, length as m-dash]O); 27.41; 27.31; 27.28 (COCH2); 8.87; 8.75; 8.54 (CH3)
38.41 (COCH2)
18.90 (–CH2CH2)
18.38 (–CH3)
8 90.60 51.21 70.62 67.34 69.88 61.45 169.80 (C[double bond, length as m-dash]O) 172.09; 172.55; 174.06; 175.25 (C[double bond, length as m-dash]O); 27.57; 27.49; 27.36; 27.31 (CH2CO); 9.14; 9.05; 8.95; 8.91 (CH3CH2)
22.99 (COCH3)
9 α 90.46 51.21 70.44 67.21 69.98 61.45 171.21 (C[double bond, length as m-dash]O) 174.44; 173.48; 173.22; 171.66 (C[double bond, length as m-dash]O); 36.00; 35.99; 35.86; 35.85 (COCH2); 18.40; 18.32; 18.29; 18.23 (CH2); 13.58; 13.55; 13.49 (CH3)
29.47 (COCH2)
9.49 (CH3)
β 92.66 52.87 73.14 67.44 72.35 61.46 171.22 (C[double bond, length as m-dash]O) 171.66; 173.23; 173.49; 173.77 (C[double bond, length as m-dash]O); 35.85; 35.86; 35.99; 36.01 (COCH2); 18, 24; 18.29; 18.33; 18.41 (CH2); 13.42; 13.5; 13.55; 13.58 (CH3)
29.69 (COCH2)
9.63 (CH3)
10 α 90.52 52.84 70.19 67.04 69.42 61.53 167.39 (C[double bond, length as m-dash]O) 170.63; 169.99; 169.75; 169.49; 169.44; 169.28; 168.60 (C[double bond, length as m-dash]O); 20.94; 20.73; 20.69; 20.61; 20.57; 20.36 (CH3)
134.44 (CH)
131.17 (C)
123.71 (CH)
β 89.80 53.53 70.53 68.36 72.66 61.56
11 α 90.43 52.90 70.29 66.84 69.21 61.39 167.31 (C[double bond, length as m-dash]O) 174.00; 173.37; 173.08; 172.83172.74; 172.03 (C[double bond, length as m-dash]O); 27.48; 27.29; 27.27; 27.20 (COCH2); 20.93; 15.18; 14.12; 8.91; 8.85; 8.78; 8.54; 8.45 (CH3)
134.37 (CH)
132.12 (C)
123.58 (CH)
β 89.72 53.60 68.16 65.75 72.83 60.29
12 α 90.33 52.97 70.30 66.82 69.10 60.38 167.33 (C[double bond, length as m-dash]O) 173.21; 172.50; 172.20; 171.95; 171.93; 171.82; 171.19; 171.08 (C[double bond, length as m-dash]O); 35.95; 35.88; 35.85; 35.74; 35.66; 29.67 (COCH2); 18.28; 18.21; 18.19; 18.11; 18.07; 17.96; 17.90 (CH2); 14.17; 13.61; 13.59; 13.57; 13.52; 13.42; 13.21; 13.12 (CH3)
134.39 (CH)
131.26 (C)
123.59 (CH)
β 89.67 53.71 70.20 68.13 72.80 61.43
13 90.61 51.00 70.61 67.56 69.66 61.53 171.55 (C[double bond, length as m-dash]O) 170.57; 169.99; 169.02; 168.57 (C[double bond, length as m-dash]O); 22.87; 20.79; 20.58; 20.56 (CH3)
20.44 (CH3)
14 90.60 51.09 70.61 67.32 69.88 61.47 172.08 (C[double bond, length as m-dash]O) 175.18; 174.05; 173.55; 172.55 (C[double bond, length as m-dash]O); 27.52; 27.47; 27.34; 27.30 (COCH2); 9.08; 9.04; 8.97; 8.90 (CH3)
29.49 (COCH2)
9.57 (CH3)
15 90.44 51.25 70.40 67.26 70.00 61.48 174.48 (C[double bond, length as m-dash]O) 173.27; 172.73; 171.71; 171.24 (C[double bond, length as m-dash]O); 38.38; 36.06; 36.02; 35.91 (COCH2); 18.89; 18.44; 18.33; 18.28 (–CH2CH2); 13.63; 13.60; 13.58; 13.56 (–CH3)
18.28 (–COCH2)
35.89 (–CH2CH2)
13.55 (–CH3)
18 92.31 52.92 67.86 72.43 72.84 61.66 18.12 (CH3); 46.95 (CH); 128.36 (2C; CH); 128.59 (CH); 129.0 (CH); 129.18 (CH); 130.05 (2C, CH); 131.15 (CH); 132.63 (CH); 137.32 (C); 138.03 (C); 141.34 (C); 173.67 (C[double bond, length as m-dash]O); 196.43 (C[double bond, length as m-dash]O). 169.25; 169.42; 170.61; 170.94 (C[double bond, length as m-dash]O); 20.44; 20.52; 20.65; 20.71 (CH3)

Analysis of the NMR spectra of compounds 7 and 9 showed that the H-1 signal of α-anomer appeared at higher δ values than the H-1 signal of β-anomer, owing to their different equatorial and axial orientations (Δδ ∼ 0.5 ppm). Meanwhile, the C-1 carbon atom of the α-anomer resonated at higher field than of the β-anomer (Δδ ∼ 2.1 ppm). Especially, the H-1 chemical shifts of the α-anomer of N,N-phthaloyl glucosamine derivatives were lower than chemical shifts of the β-anomer. This showed that influence of two carbonyl groups (C[double bond, length as m-dash]O) and benzene ring in N,N-phthaloyl glucosamine structure caused deshielding of H-1 in the β-anomer (Δδ ∼ 0.22 ppm) in comparison with the corresponding H-1 signal of the α-anomer. In this case, the C-1 carbon atom of the α-anomer resonated at lower fields than C-1 carbon atom of the β-anomer (Δδ ∼ 0.7 ppm). Interestingly, the various N-acyl substituted groups had a significant influence on the resonance frequency of the sugar ring protons and carbons.

Analysis of the NMR spectra of 1–4 confirmed the empirical rules in the NMR spectroscopy of carbohydrates. Firstly, the axial orientation of the anomeric OH group in the α-anomer caused absorption at higher δ values of equatorially oriented H-1 protons in comparison with the corresponding β-anomer (Δδ ∼ 0.5 ppm). The C-1 carbon atom of the β-anomer resonated at lower fields than the C-1 carbon atom of the α-anomer (Δδ ∼ 4 ppm). These were compatible with the previous report.26 Moreover, the C-2 carbon atom of the β-anomer was deshielded in comparison with the corresponding C-2 carbon atom of the α-anomer (Δδ ∼ 2.5 ppm).

Experimental

General methods

Melting points were measured with a Electrothermal Model 9200 (England). The 1H and 13C NMR spectra (CDCl3, d6-DMSO or D2O, internal TMS) were measured with a Bruker Avance 500 NMR Spectrometer. Optical rotations were measured on a Polarimeter Model ADP 220 (Bellingham – Stanley Ltd, England) in a 1 cm3 cell at 20 °C. Thin layer chromatography (TLC) was performed on the E. Merck Kieselgel 60 F-254 plates using the following eluent system (v/v) 1[thin space (1/6-em)]:[thin space (1/6-em)]1 petroleum ether – AcOEt and visualized by treatment with an acidic solution of 10% H2SO4 and EtOH. Flash chromatography was performed with Silica Gel 60 (230–400 mesh, E Merck, Darmstadt, Germany).

Procedure for the synthesis of 1,3,4,6-tetra-O-acyl-N-acyl-D-glucosamine derivatives and penta-acyl-D-glucosamine derivatives

General procedure for synthesis of N-acyl-D-glucosamine derivatives (1–4). Sodium (8.0 g, 34.8 mmol) was added slowly to 50 mL of anhydrous methanol followed by 5.0 g (23.2 mmol) of Glu·HCl under nitrogen atmosphere. The solution was stirred for 15 min and the precipitate was filtered off. To this filtrate, anhydride acid (34.8 mmol) was added under nitrogen atmosphere. The reaction mixture was stirred at room temperature for 1 h and then cooled to 0 °C overnight. The N-acylated compounds were collected by filtration, washed with cold methanol (25 mL), diethyl ether (50 mL) and dried at 60 °C.
N-Acetyl-D-glucosamine (1). 1H NMR (500 MHz, D2O) δ 5.17 (1H, J = 3.5 Hz), 4.68 (1H, d, J = 8.5 Hz), 3.8 (2H, m), 3.74 (2H, dd, J = 7.0, 2.5 Hz), 3.69 (2H, ddd, J = 15.5, 5.5, 1.5 Hz), 3.62 (2H, dd, J = 10.0, 8.5 Hz), 3.42 (2H, m), 2.02 (6H, s). 13C NMR (125 MHz, D2O) δ 174.80, 174.54, 94.98, 90.89, 76.00, 73.59, 71.62, 70.74, 70.14, 69.91, 60.81, 60.66, 56.76, 54.13, 22.23, 21.96.
N-Propyl-D-glucosamine (2). 1H NMR (500 MHz, D2O) δ 5.17 (1H, J = 3.5 Hz), 4.66 (1H, d, J = 12.0 Hz), 3.90–3.71 (8H, m), 3.65 (2H, m), 3.5 (1H, m), 3.43 (1H, m), 2.32–2.26 (4H, q, 7.5 Hz), 1.12–1.08 (6H, t, 7.5 Hz). 13C NMR (125 MHz, D2O) δ 178.77, 178.55, 95.04, 90.95, 76.02, 73.93, 71.65, 70.72, 70.20, 69.98, 60.84, 60.69, 56.67, 54.03, 29.43, 29.12, 9.55, 9.50.
N-Butyl-D-glucosamine (3). 1H NMR (500 MHz, D2O) δ 5.16 (1H, d, J = 3.5 Hz), 4.67 (1H, d, J = 10.5 Hz), 3.80 (6H, m), 3.69 (2H, ddd, J = 30.5, 11.5, 5.0 Hz), 2.22 (4H, m), 1.55 (4H, m), 0.86 (6H, m). 13C NMR (125 MHz, D2O) δ 177.82, 177.59, 95.04, 90.93, 75.98, 73.87, 71.61, 70.61, 70.22, 70.00, 60.82, 60.67, 56.62, 54.03, 38.03, 37.63, 19.01, 12.69.
N,N-Phthaloyl-D-glucosamine (4). 1H NMR (500 MHz, D2O) δ 7.67 (4H, m), 7.52 (4H, d, 2.5 Hz), 5.39 (1H, d, 3 Hz), 4.87 (1H, d, 8.5 Hz), 3.87–3.62 (8H, m), 3.43 (2H, m), 3.22 (2H, dd, J = 10, 9 Hz). 13C NMR (125 MHz, D2O) δ 174.18, 133.92, 130.83, 128.8, 92.79, 89.19, 76.23, 72.05, 71.66, 69.77, 69.66, 60.55, 60.42, 56.82, 54.38.
General procedure for synthesis of N-acyl-1,3,4,6-tetra-O-acyl-D-glucosamine derivatives (5–12). A round-bottomed flask equipped with a three-way stopcock was heated under reduced pressure and then cooled room temperature under a nitrogen atmosphere. N-acyl glucosamine (4.52 mmol), pyridine (10 mL) and anhydride acid (27.12 mmol) were replaced in the flask. The mixture was stirred at room temperature for 10 h. The cold water was then added and the resulting solution was extracted with ethyl acetate. The organic layer was washed with saturated NaHCO3 aqueous solution, brine, dried over MgSO4 and concentrated in vacuo to provide the desired products.
General procedure for synthesis of penta-acyl-D-glucosamine derivatives (13–15). Using the same procedure as described for compounds 5–12, with replacement of N-acyl glucosamine by Glu·HCl.

Procedure for the synthesis of glucosamine conjugated with ketoprofen

Synthesis of N-((p-methoxyphenyl)methyliden)-1,3,4,6-tetra-O-acetyl-2-deoxy-2-amino-β-D-glucopyranose (16). Into a round-bottomed flask were introduced 20.0 g of GlcN·HCl (92.76 mmol) and 100 mL of NaOH solution (1 M). After cooling down to 0 °C, 13.5 mL of p-anisaldehyde was added via dropwise under stirring. The resulting mixture was maintained at 0 °C for 1 h. The residue was collected by suction filtration, washed with the cold water, the cold ethanol, diethyl ether and dried in vacuo to give N-((p-methoxyphenyl)methyliden)-2-deoxy-2-amino-D-glucopyranose as a white solid (22.3 g, 80.87%).

A round-bottomed flask equipped with a three-way stopcock was heated under reduced pressure and then cooled room temperature under a nitrogen atmosphere. The above intermediate (22.3 g, 75.03 mmol) and pyridine (120 mL) were placed in the flask. After cooling down to 0 °C, acetic anhydride (12.5 mL) was added under stirring via a syringe. The mixture was stirred at 0 °C during 2 h and stirring was continued at room temperature overnight. The reaction was ended by adding 500 mL the water at 0 °C. The residue was collected by suction filtration, washed with the cold water and dried in vacuo to give 16 as a white solid (28.7 g, 83.87%). 1H NMR (500 MHz, CDCl3) δ 7.65 (2H, dd, J = 7.0, 2.0 Hz), 6.92 (2H, dd, J = 9.0, 2.0 Hz), 5.93 (1H, d, J = 8 Hz), 5.43 (1H, t, 10 Hz), 5.14 (1H, t, J = 10 Hz), 4.36 (1H, dd, J = 12.5, 4.5 Hz), 4.12 (1H, dd, J = 12.5, 2.5 Hz), 3.96 (1H, m), 3.84 (3H, s), 3.43 (1H, dd, J = 10.0, 8.0 Hz), 2.13–1.88 (12H, s). 13C NMR (125 MHz, CDCl3) δ 170.68, 169.89, 169.54, 168.76, 164.27, 130.27, 128.35, 114.09, 93.20, 73.30, 72.98, 72.81, 68.11, 61.87, 55.42, 20.81, 20.76, 20.68, 20.51.

Synthesis of 1,3,4,6-tetra-O-acetyl-β-D-glucosamine hydrochloride (17). A 28.0 g (60.0 mmol) sample of 16 was dissolved in acetone (200 mL). Then 12.5 mL of aq. HCl (5 M) was added. After 30 min, diethyl ether was added to the reaction mixture and stirring for 1 hour. The residue was collected by suction filtration, washed with the cold diethyl ether and dried in vacuo to give the product 17 (20.2 g, 91.3%). 1H NMR (500 MHz, d6-DMSO) δ 8.85 (3H, s), 5.91 (1H, d, J = 8.5 Hz), 5.37 (1H, t, J = 9.5 Hz), 4.92 (1H, t, J = 9.5 Hz), 4.17 (1H, dd, J = 12.0, 4.0 Hz), 3.99 (2H, m), 3.54 (1H, t, J = 9.5 Hz), 2.17–1.97 (12H, s). 13C NMR (125 MHz, d6-DMSO) δ 169.89, 169.70, 169.25, 168.56, 90.07, 71.58, 70.32, 67.82, 61.23, 52.14, 20.88, 20.79, 20.41, 20.27.
Synthesis of N-(2-(3-benzoylphenyl)propanoyl)-1,3,4,6-tetra-O-acetyl-2-deoxy-2-amino- β-D-glucopyranose (18). A 6.0 g (16.2 mmol) sample of 17 was dissolved in CH2Cl2 (80 mL). Then 80 mL of Na2CO3 solution (1 M) was added. After 30 min, the mixture was extracted with CH2Cl2. The organic layer was washed with water, dried over anhydrous MgSO4 and concentrated under reduced pressure to give 1,3,4,6-tetra-O-acetyl-β-D-glucosamine as a white solid (5.1 g, 92.8%). Mp (138 °C).

A round-bottomed flask equipped with a three-way stopcock was heated under reduced pressure and then cooled room temperature under a nitrogen atmosphere. Ketoprofen (1.0 g, 3.9 mmol) in dry DMF (15 mL) and DCC (1.22 g, 5.8 mmol) were placed in the flask and the mixture was stirred at 0 °C. Into the flask was added 1,3,4,6-tetra-O-acetylglucosamine (0.5 g, 1.5 mmol) in dry DMF via a syringe. The whole was stirred at 0 °C for 4 h and stirring was continued at room temperature overnight. The mixture was diluted by ethyl acetate and then the solid was filtered off. Ethyl acetate layer was washed with water, dried over anhydrous MgSO4 and concentrated under reduced pressure. The pure product 18 was recrystallized in diethyl ether as a white solid (0.44 g, 51.5%).

Conclusions

We synthesized successfully five novel tetra-O-acyl-N-acyl-D-glucosamine derivatives 7, 9, 11, 12, 18 with a good yield. The most important influence of α- and β-anomer ratio was related to acyl group at the amine (–NH2) position and at O-acyl group of C-1 carbon position. Synthesis of substituent acyl groups containing longer carbon chain and the testing of biological activities of compounds 5–12 and 18 were planned.

Acknowledgements

We thank Prof. Dr Chu Pham Ngoc Son (President of Chemical Society of Ho Chi Minh City) for NMR spectra analysis.

References

  1. V. Majithia and S. A. Geraci, Am. J. Med., 2007, 120, 936–939 CrossRef PubMed.
  2. C. Turesson, W. M. O'Fallon, C. S. Crowson, S. E. Gabriel and E. L. Matteson, Ann. Rheum. Dis., 2003, 62, 722–727 CrossRef CAS.
  3. J. A. A. A-Zubieta, H. K. Choi, M. Sadatsafavi, M. Etminan, J. M. Esdaile and D. Lacaille, Arthritis Rheum., 2008, 59, 1690–1697 CrossRef PubMed.
  4. K. Nishimura, D. Sugiyama, Y. Kogata, G. Tsuji, T. Nakazawa, S. Kawano, K. Saigo, A. Morinobu, M. Koshiba, K. M. Kuntz, I. Kamae and S. Kumagai, Ann. Intern. Med., 2007, 146, 797–808 CrossRef.
  5. T. Towheed, L. Maxwell, T. P. Anastassiades, B. Shea, J. B. Houpt, V. Welch, M. C. Hochberg and G. A. Wells, Glucosamine therapy for treating osteoarthritis; ed. C. Musculoskeletal, John Wiley & Sons, New York, U.S.A, 2009, 4, pp. 3–10 Search PubMed.
  6. M. G. Buse, Am. J. Physiol., 2006, 290, E1–E8 CAS.
  7. J. Cibere, J. A. Kopec, A. Thorne, J. Singer, J. Canvin, D. B. Robinson, J. Pope, P. Hong, E. Grant and J. M. Esdaile, Arthritis Rheum., 2004, 51, 738–745 CrossRef CAS PubMed.
  8. F. Richy, O. Bruyere, O. Ethgen, M. Cucherat, Y. Henrotin and J. Y. Reginster, Arch. Intern. Med., 2003, 163, 1514–1522 CrossRef CAS PubMed.
  9. I. Brockhausen, J. Carran, K. McEleney, M. Lehotay, X. Yang, L. Yin and T. Anastassiades, Carbohydr. Res., 2005, 340, 1997–2003 CrossRef CAS PubMed.
  10. K. Azuma, T. Osaki, T. Wakuda, T. Tsuka, T. Imagawa, Y. Okamoto and S. Minami, Inflammation, 2012, 35, 1462–1465 CrossRef CAS PubMed.
  11. N. Elmouelhi, U. Aich, V. D. P. Paruchuri, M. A. Meledeo, C. T. Campbell, J. J. Wang, R. Srinivas, H. S. Khanna and K. J. Yarema, J. Med. Chem., 2009, 52, 2515–2530 CrossRef CAS PubMed.
  12. M. W. Poustie, J. Carran, K. McEleney, S. J. Dixon, T. P. Anastassiades and S. M. Bernier, J. Pharmacol. Exp. Ther., 2004, 311, 610–616 CrossRef CAS PubMed.
  13. J. M. Hermandez-Torres, S. T. Liew, J. Achkar and A. Wei, Synthesis, 2002, 487–490 CrossRef PubMed.
  14. Y. Inouye, K. Onodra, S. Kitaoka and S. Hirano, J. Am. Chem. Soc., 1956, 78, 4722–4724 CrossRef.
  15. U. Aich, C. T. Campbell, M. B. Jones, S. G. Sampathkumar and K. J. Yarema, US Pat., 0144653 (A1), 2010.
  16. S. Sampathkumar, M. B. Jones, M. A. Meledeo, C. T. Campbell, S. S. Choi, K. Hida, P. Gomutputra, A. Sheh, T. Gilmartin, S. R. Head and K. J. Yarema, ACS Chem. Biol., 2006, 13, 1265–1275 CAS.
  17. S. J. Warden, The Physician and Sports Medicine, 2010, 38, 132–138 Search PubMed.
  18. S. Trelle, S. Reichenbach, S. Wandel, P. Hildebrand, B. Tschannen, P. M. Villiger, M. Egge and P. Juni, Br. Med. J., 2011, 342, c7086 CrossRef PubMed.
  19. P. M. Kearney, C. Baigent, J. Godwin, H. Halls, J. R. Emberson and C. Patrono, Br. Med. J., 2006, 332, 1302–1308 CrossRef CAS PubMed.
  20. R. K. Uhrig, M. A. Picard, K. Beyreuther and M. Wiessler, Carbohydr. Res., 2000, 325, 72–80 CrossRef CAS.
  21. J. Borowiecka and A. Stanczak, Il Farmaco, 2001, 56, 257 CrossRef CAS.
  22. Y. C. Zhang, Y. X. Li and H. S. C. Guan, Chem. Lett., 2005,(2), 179–182 Search PubMed.
  23. M. S. Macauley, G. E. Whitworth, A. W. Debowski, D. Chin and D. J. Vocadlo, J. Biol. Chem., 2005, 280, 25313–25322 CrossRef CAS PubMed.
  24. T. Q. Ho, T. D. H. Nguyen, T. D. Nguyen, C. H. Dang and C. H. Nguyen, Vietnam J. Chem., 2010, 48(4A), 676–682 Search PubMed.
  25. V. R. Krishnamurthy, A. Dougherty, M. Kamat, X. Song, R. D. Cummings and E. L. Chaikof, Carbohydr. Res., 2010, 345, 1541–1547 CrossRef CAS PubMed.
  26. Y. Chen, S. Luo, S. Hung, S. I. Chan and D. M. Tzou, Carbohydr. Res., 2005, 340, 723–729 CrossRef CAS PubMed.

Footnote

† Electronic supplementary information (ESI) available: 1D and 2D NMR data of novel compounds. See DOI: 10.1039/c3ra46007j
This journal is © The Royal Society of Chemistry 2014
Click here to see how this site uses Cookies. View our privacy policy here.