Gibberelline—lxii: Synthese von 7-desoxygenierten gibberellin-a3-verbindungen

Reaction sequences leading to GA₃ derivatives with stepwise deoxygenated position 7 have been reported. From four different methods studied for the synthesis of GA₃-7-alcohols the direct NaBH₄-reduction of the anhydrides5a and5b has been found to be optimal leading in good yields to 3 and 9, respectively. Oxidation of 3 with the N - chlorosuccinimide - dimethylsulfide complex or pyridinium chlorochromate followed by deacetylation afforded the GA₃-7-aldehyde 16.—The partial synthesis of 6β-methyl-7-nor-GA₃20 has been realized starting from 3 via the iodinemethyl compound 18 and its reduction with (C₂H₅)₃SnH or Na₂Fe(CO)₄] to19 and subsequent saponification.—The structures of the new gibberellin derivatives were determined on the basis ofIR, ¹H-NMR and MS data.