Protoemetinol synthesis

The homoallylic acetal radical cyclization product reported by Stork [55] was later used in the construction of a significant portion of the gelsemine structure [76]. Further examples for homoallylic acetal cyclization exhibiting useful stereoselectivity include the (-)-protoemetinol synthesis by Fukumoto [77] and the rhizoxin partial syntheses by Rama Rao [78] and White [79]. In the synthesis of (+)-12b-epidevinylantirhine (117) [80] (Scheme 40), Ihara adopted low-temperature conditions for radical cyclization of the chiral unsaturated ester 114 in the presence of MAD. The lactone 116 in high diastereomeric excess was obtained from the cycli-... 

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