C19 gibberellins

An interesting biomimetic chemical conversion of the C20 gibberellins into the C19 gibberellins by decarboxylation of C-20 acids with lead tetra-acetate has been described.The selective reduction of the C-7 carboxy-group of the gibberellins has been achievedby the reduction of the dimeric anhydrides with sodium borohydride. A number of amides of gibberellins Ai and A3 have been described. 

The final fate of C-20, which is lost during the biosynthesis of the C19 gibberellin lactones, is as carbon dioxide. Gibberellin A13 aldehyde may be an intermediate in gibberellin biosynthesis prior to this step. The conversion of gibberellin A9 into gibberellin A20 in excised lettuce hypocotyls has been observed. " Gibberellins Ag, Aie, and A24 and abscisic acid have been detected by g.c.-m.s. in rye. 

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