Trisubstituted gem-dimethyl

Selenium dioxide reveals a useful stereoselectivity when applied to trisubstituted gem-dimethyl alkenes. The products are predominantly the Zs-allylic alcohol or... 

The first total syntesis of cristatic acid, a potent antibiotic against Gram-positive bacteria, was reported by A. Furstner et al." " The prenylated aromatic substrate (trisubstituted gem-dimethyl alkene) was subjected to a Se02-catalyzed allylic oxidation to obtain stereospecifically the ( )-allylic alcohol. 

Another fairly general observation that can be reconciled with the intervention of allylic intermediates is that dienes are usually obtained rather than the alcohol, if the latter would be tertiary. As illustrated by the last entry in Scheme 9.15, the reaction reveals high stereoselectivity when applied to trisubstituted gem-dimethyl... 

Selenium dioxide oxidation reveals a very high and useful selectivity when applied to trisubstituted gem-dimethyl olefins. The products are always predominantly the -allylic alcohol or unsaturated aldehyde.This stereoselectivity... 

They also report that the oxidation of gem-dimethyl trisubstituted olefins with selenium dioxide in aqueous ethanol proceeds stereospecifically to give rrorw-alcohols... 

The lactone-directed intramolecular Diels-Alder cycloaddition was the key step in D.F. Taber s synthesis of trans-dihydroconfertifolin. During the endgame, the Simmons-Smith cyclopropanation was utiiized to install the gem-dimethyl group at C4. The trisubstituted alkene was cyclopropanated in excellent yield and the resulting cyclopropane was subjected to catalytic hydrogenation. 

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