Synthesis and absolute configurations of the naturally occurring 3- and 4-methylmuconolactones: X-ray structures of (S)-1-phenylethylammonium salts and an 8-bromo-1-methyl-muconodilactone
作者:Andrew A. Freer、Gordon W. Kirby、Ghanakota V. Rao、Ronald B. Cain
DOI:10.1039/p19960002111
日期:——
(±)-3-Methylmuconolactone (±)-4 is resolved by fractional crystallisation of the (S)-(–)-1-phenylethylammonium salts. The X-ray crystal structures of both salts are determined. Salt A (Fig. 1) gives (S)-(–)-3-methylmuconolactone 4, which is identical to the lactone from fungi. The lactone is converted with bromine into the bromo dilactone 5 and thence with tributyltin hydride into the (–)-1-methylmuconodilactone
(±)-3-甲基粘康内酯(±)-4通过(S)-(-)-1-苯基乙基铵盐的分步结晶而分离。确定了两种盐的X射线晶体结构。盐A(图1)得到(S)-(-)-3-甲基粘康内酯4,与真菌中的内酯相同。内酯由溴转化为溴代双内酯5,然后与三丁基锡氢化物转化为(-)-1-甲基粘康二内酯6。该双内酯与氢氧化钠水溶液可制得(S)-(+)-4-甲基粘康内酯3,这是相同的细菌内酯以及(S)-(-)-3-甲基粘康内酯4。溴代双内酯5的X射线结构(图3)证实了真菌和细菌粘康内酯的绝对构型。(S)-(+)-4-甲基粘康内酯3得到相应的(-)-溴二内酯9,也可用氢化三丁基锡还原,得到(-)-1-甲基粘康二内酯6。溴二内酯异构体(±)-5类似地,分别通过相应的2-溴粘康内酯(±)-7和10将二甲基双内酯(±)-8和11转化成二溴二内酯(±)-8和11 。