PHOTOCYCLIZATION OF ENAMIDES .39. GENERAL STRATEGY FOR THE SYNTHESIS OF PSEUDODISTOMINS - SYNTHESIS OF TRIACETATES OF (+ -)-TETRAHYDROPSEUDODISTOMIN AND PROPOSED STRUCTURES OF PSEUDODISTOMIN-A AND PSEUDODISTOMIN-B/

A synthetic strategy of pseudodistomin was developed by first synthesi zing the (+/-)-(2 alpha,4 beta,5 beta)-5-amino-2(3-hydroxypropyl)piper idin-4-ol 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 a-acylamino photo-induced radi cal allylation by allyltributyltin replacing a methylsulfanyl group, T he key intermediate 14 was then converted into the piperidines 19 and 20, with a dienyl side-chain, which have the structures proposed for p seudodistomins A 1 and B 2. However, direct comparisons with the triac etates of the natural alkaloids have shown that a revision of the prop osed structures is required.