Reconstruction of pyrrolo[2,3-b]indoles carrying an alpha-configured reverse C3-dimethylallyl moiety by using recombinant enzymes.

Nine reversely C3-prenylated pyrrolo[2,3-b]indoles were successfully prepared by using two recombinant enzymes involved in the biosynthesis of acetylaszonalenin from Neosartorya fischeri. The prenyltransferase AnaPT catalysed the conversion of six tryptophan-containing cyclic dipeptides to reversely C3-prenylated indoline derivatives. Using cyclo-L-Trp-L-Trp as substrate, both mono- and diprenylated indolines were obtained. Two of the AnaPT products were acetylated at position N1 by the acetyltransferase AnaAT. The structures of the obtained compounds were characterised by HR-ESI-MS, (1)H- and (13)C-NMR analyses as well as by long-range (1)H-(13)C connectivities in heteronuclear multiple-bond correlation (HMBC) spectra after preparative isolation. Their absolute configurations were determined by analysing the (1)H-(1)H spatial correlations in rotating-frame nuclear overhauser effect spectroscopy (ROESY).