A concise sequential photochemical-metathesis approach for the synthesis of (+)-castanospermine and possible uniflorine-A stereoisomers

A recently developed strategy for polyhydroxylated indolizidine ring construction has been applied to the synthesis of (+)-castanospermine and possible isomers of uniflorine-A. The routes to these targets rely on the use of the earlier discovered photocyclization reaction of pyridinium perchlorate in a concise route for preparation of a key N-allylacetamidocyclopentendiol intermediate. Ring rearrangement metathesis of this substance gives an allyl-tetrahydropyridine, which is then transformed to the targets by execution of regio- and stereo-controlled hydroxylation processes followed by indolizidine ring construction.