Gibberellin degradation products

Gibberellins and their degradation products possess characteristic tetracyclic carbon frameworks. I synthesized ( )-14,13 ( )-15,14 ( )-16,15 and ( )-1716 (Figure 2.4). In this section I will detail the synthesis of ( )-epigibberic acid (18), completed in October 1962, just a month before my wedding ceremony with my wife Keiko nee Suzuki).17,18... 

Schneider et al. (1965) have discussed the gibberellins, their derivatives and degradation products, and have given UV, ORD, NMR, and IR data. 

Chloro-3-methyl-4-nitro-lH-pyrazole (Release) has no auxin-, gib-berellin-, or cytokinin-like activity, yet it is an ejffective abscission agent. At the present, there is no evidence to indicate that Release retards auxin, gibberellin, or cytokinin activity. It does stimulate and enhance the tissue production of ethylene (105). Release is fairly stable, and there is no indication that it is degraded by the tissue to ethylene per se (106). 

Attempts have been made to determine why a-amylase synthesis eventually declines in the intact grain (e.g. see the decline in rate of a-amylase synthesis in Figure 7.4A and B after three and two days respectively). One possible reason is that production of the stimulus (i.e. GA) for a-amylase synthesis decreases, perhaps because hormonal synthesis is itself inhibited by the products of starch degradation. Unequivocal evidence supporting this possibility is lacking. In any case, sufficient gibberellin is released into the endosperm during the first one or two days after the start of imbibition to support a-amylase synthesis for at least four to five days thereafter (Fig. 7.4 C). Thus any limitation in GA synthesis after one or two days is unlikely to affect enzyme production. 

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