Partial synthesis of [1β,2β-2H2]-, [2β-2H]-, and [2α-2H]-Gibberellin A1

Abstract

The preparation of [1β-2β-²H₂]GA₁ by [²H]hydrogenation of GA₃ 13-acetate 16,17-epoxide is described. [2β-²H]Gibberellin A₁ was prepared by [²H]hydrogenolysis of GA₃ 13-acetate methyl ester, iodolactonisation of the 2β-deuteriated product followed by reduction and hydrolysis. Treatment of [2β-²H]-1β-iodoGA₁ 13-acetate with 1,8-diazabicyclo[5.4.0]undec-7-ene gave [2-²H]GA₃ 13 -acetate which has been reduced to [2α-²H]GA₁ either via hydrogenation of the corresponding 16,17-epoxide or by hydrogenolysis, iodolactonisation, and reduction. The isotopic labelling, assigned by a combination of ¹H, ²H, and ¹³C n.m.r. spectroscopy, was completely stereoselective in all cases.