The structures of two new gibberellins (GA105 and
GA108) from developing apple seeds were confirmed as
2β- and 11β-hydroxy-9,15-cyclo-GA9,
respectively, by synthesis of their methyl esters (7) and (8); the analogous
1α-, 2α- and 11α-isomers were also prepared, the last two
being identified as metabolites of 9,15-cyclo-GA9 (2)
formed in feeding experiments with fern prothallia of
Lygodium circinnatum. The route to (7) began with the
Birch reduction of gibberellic acid (GA3) methyl ester
3,13-dimesylate, thereby removing the oxygen substituents from C3 and C13. A
series of iodolactonizations and elimination processes followed by ozonolysis
of the 17-methylene group furnished (19) which, on treatment with potassium
hydride, underwent intramolecular alkylation to afford the cyclogibberellin
(20). Further functional group manipulation then led to (7) via its
2α-epimer (23). The previously prepared 11β-bromocyclogibberellin
(28) was also subjected to a series of functional group manipulations and
deletions to afford the 11α-hydroxy analogue (33), and thence the
11β-epimer (8) by means of an oxidation/reduction cycle;
1α-hydroxycyclo-GA9 methyl ester (26) was
similarly prepared from the methyl ester of the known 1β-epimer (3).
从发育中的苹果种子中提取的两种新赤霉素(GA105 和 GA108
GA105 和 GA108)的结构被证实为
2β-和 11β-羟基-9,15-环-GA9、
通过合成它们的甲酯 (7) 和 (8),分别确认它们是 2β- 和 11β- 羟基-9,15-环-GA9;类似的
1α-、2α- 和 11α- 异构体也被制备出来,最后两种
被确定为 9,15-环-GA9(2)的代谢物。
的蕨类原叶喂食实验中形成的代谢物。
Lygodium circinnatum。获得 (7) 的途径始于
桦木还原赤霉素(GA3)甲酯
3,13-二甲酸酯,从而去除 C3 和 C13 中的氧取代基。A
一系列碘内酯化和消除过程,然后通过臭氧分解
生成了 (19)。
氢化钾处理后,发生分子内烷基化反应,得到环赤霉素(20)。
(20).进一步的官能团操作后,(7)通过其
2α-epimer (23)。之前制备的 11β-溴环赤霉素
(28) 也进行了一系列的官能团操作和缺失
通过一系列的官能团操作和缺失,得到了 11α-hydroxy 类似物 (33),然后又得到了
11β-epimer (8);
1α-羟基环-GA9 甲酯(26)
同样,1α-羟基环-GA9 甲酯(26)也是由已知的 1β-epimer (3) 的甲酯制备而成。