Gibberellin A3 has been converted to
3α-methylGA20 8 in 33% yield via
catalytic hydrogenation of the 3-exo-methylene derivative 14. In an
attempt to prepare 3β-methylGA20 9, the
3α-methanesulfonate 25 has been treated with lithium
dimethylcuprate; only the β-keto sultones 26 and 27 have been
isolated (84% yield). In contrast, under similar conditions the
3α-methanesulfonate 35 gave the 2-oxopropylsulfonyloxy derivatives
36 and 37. Synthesis of 3β-methylGA20 has been achieved
via reaction of the 3α-trifluoromethanesulfonate
38 with lithium dimethylcuprate. 3α-MethylGA20 and
3β-methylGA20 show similar activity to GA20
(and significantly less activity than GA3) in the stimulation
of stem elongation of dwarf rice seedlings.
赤霉素 A3 通过 3-外亚甲基衍
生物 14 的催化氢化转化为 3δ-甲基GA20 8,收率为 33%。在制备 3δ-甲基 GA20 9 的尝试中,3δ-
甲磺酸盐 25 用二甲基杯酸
锂进行处理;只分离出了δ-酮素酮 26 和 27(产率为 84%)。相反,在类似条件下,3δ-
甲磺酸盐 35 得到了 2-氧代丙基磺酰氧基衍
生物 36 和 37。通过 3δ-
三氟甲磺酸 38 与二甲基杯酸
锂的反应,合成了 3δ-甲基-GA20。3 δ-甲基-GA20和 3 δ-甲基-GA20在刺激矮小
水稻秧苗茎伸长方面的活性与 GA20 相似(但明显低于
GA3)。