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.