Open-chain benzyl-ether-protected polyols in which one of the alcohols is either allylic or benzylic are synthesised by addition of organometallic vinyl or phenyl reagents to benzyl- ether-protected carbohydrate hemiacetals. The diastereoselectivity of addition is dependent on whether a Grignard reagent or a trialkylzincate reagent is used. The open-chain compounds undergo a stereospecific cyclisation reaction on treatment with catalytic strong ...
