2β-Alkyl derivatives of gibberellin A1
Abstract
In the reaction of gibberellin A3(1) with lithium dialkylcuprates, anti-SN2′-type substitution occurred with the displacement of the lactone function. The resultant 2β-alkyl-1(10)-enedioic acids (4)–(7) were iodolactonised, then reductively de-iodinated to give 2β-methyl, 2β-ethyl, 2β-n-propyl, and 2β-n-butyl gibberellin A1(16)–(19). The reaction of lithium dimethylcuprate with 3-didehydrogibberellin A3 was complex but there was no evidence for the occurrence of conjugate addition to the α,β-unsaturated ketone in competition with the anti-SN2′-type reaction.