SCHEDULED MAINTENANCE
Allylic chlorination of gibberellins A3 and A7 methyl esters and of gibberellin A3: preparation of gibberellin A5
Abstract
A high-yield conversion of gibberellin A3 to gibberellin A5 is described. With thionyl chloride, gibberellin A3 methyl ester gives mainly 1β-chlorogibberellin A5 methyl ester; the isomeric 3α-chloro-1-ene was the main product from the reaction with toluene-p-sulphonyl chloride and lithium chloride. Each product is reduced by tri-n-butylstannane and acetylated to give the same mixture of the 13-acetates of gibberellin A5 methyl ester and of the isomeric 1(10)-ene-19,2-lactone. Hydrolysis of gibberellin A5 methyl ester 13-acetate gives gibberellin A5 in 20% overall yield from gibberellin A3. [1-2H1]Gibberellin A5 is obtained in the same way by using tri-n-butyl-[2H1]stannane in the reduction step. Analogous chlorination products of gibberellin A7 methyl ester and of gibberellin A3 are described.
Please wait while we load your content...
