Stereospecific synthesis of aszonalenins by using two recombinant prenyltransferases

In previous studies, two prenyltransferases were overproduced and characterised biochemically. AnaPT from Neosartorya fischeri is involved in the biosynthesis of acetylaszonalenin and was shown to catalyse the C3-prenylation of (R)-benzodiazepinedione (6). CdpNPT from Aspergillus fumigatus catalysed the N1-prenylation of different tryptophan-containing cyclic dipeptides. In this report, CdpNPT was found to catalyse the C3-prenylation of 6 and its (S)-isomer (7). Interestingly, AnaPT and CdpNPT introduced prenyl moieties from opposite sides of the indoline ring system. This feature was successfully used for the chemoenzymatic synthesis of four aszonalenin stereoisomers by using 6 and 7 as substrates and AnaPT and CdpNPT as catalysts. The stereoselectivity of the one-step reactions was about 100% and the conversion rates reached 85–100%.