Preparation of pyrrolo[2,3-b]indoles carrying a β-configured reverse C3-dimethylallyl moiety by using a recombinant prenyltransferase CdpC3PT

Abstract

Six β-configured reversely C3-prenylated pyrrolo[2,3-b]indoles were successfully prepared by using a recombinant prenyltransferase from Neosartorya fischeri. For this purpose, the putative prenyltransferase gene NFIA_074280 (termed herewith cdpC3PT) was cloned into pQE60 and overexpressed in Escherichia coli. The overproduced His₆-CdpC3PT was purified to near homogeneity and incubated with five cyclic tryptophan-containing dipeptides in the presence of dimethylallyl diphosphate (DMAPP). All of the substrates were accepted by CdpC3PT and converted to reversely C3-prenylated pyrrolo[2,3-b]indoles. Using cyclo-L-Trp-L-Trp as substrate, both mono- and diprenylated derivatives were obtained. The structures of the enzymatic products were confirmed by HR-ESI-MS, ¹H- and ¹³C-NMR analyses as well as by long-range ¹H-¹³C connectivities in heteronuclear multiple-bond correlation (HMBC) spectra after preparative isolation. ¹H-¹H spatial correlations in nuclear overhauser effect spectroscopy (NOESY) were used for determination of absolute configuration. The K_M values were determined at about 1.5 mM for DMAPP and in the range from 0.22 to 5.5 mM for cyclic dipeptides. The turnover number k_cat were found in the range of 0.023 to 0.098 s⁻¹ and specificity constants k_cat/K_M from 14.2 to 122.7 M⁻¹ s⁻¹. In contrast to the products of AnaPT bearing α-configured C3-dimethylallyl residues, the C3-prenyl moieties in the products of CdpC3PT have a β-configuration. Discovery and characterisation of CdpC3PT expand the usage of the chemoenzymatic approach for stereospecific synthesis of C3-prenylated derivatives.