Photocyclisation of enamides. Part 39. General strategy for the synthesis of pseudodistomins: synthesis of triacetates of (±)-tetrahydropseudodistomin and proposed structures of pseudodistomins A and B

Abstract

A synthetic strategy of pseudodistomin was developed by first synthesizing the (±)-(2a,4β,5β)-5-amino-2(3-hydroxypropyl)piperidin-4-o1 14 as a key intermediate via a route involving the reductive photocyclisation of enamide 5 followed by the introduction of a three-carbon side-chain by application of an α-acylamino photo-induced radical allylation by allyltributyltin replacing a methylsulfanyl group. The key intermediate 14 was then converted into the piperidines 19 and 20, with a dienyl side-chain, which have the structures proposed for pseudodistomins A 1 and B 2. However, direct comparisons with the triacetates of the natural alkaloids have shown that a revision of the proposed structures is required.