Cyclization of (+)- and (–)-S-(2-methylprop-1-enyl)-<scp>L</scp>-cysteine S-oxides
作者:John F. Carson、Robert E. Lundin
DOI:10.1039/p19760001195
日期:——
to two sulphoxides (7a), [α]D25+128°, and (7b), [α]D25–84.3°(in H2O). Cyclization in base was stereospecific. The (+)-sulphoxide (7a) yielded the axial sulphoxide, (1S,3R)-5,5-dimethyltetrahydro-1,4-thiazine-3-carboxylic acid S-oxide (9), and the (–)-sulphoxide (7b) yielded the corresponding equatorial (1R) sulphoxide (10). This establishes the absolute configurations of the acyclic sulphoxides (7a and
S-(2-甲基丙-1-烯基)-L-半胱氨酸(5)已被氧化为两种亚砜(7a),[α] D 25 + 128°和(7b),[α] D 25 –84.3° (以H 2 O计)。碱基中的环化是立体特异性的。(+)-亚砜(7a)产生轴向亚砜,(1 S,3 R)-5,5-二甲基四氢-1,4-噻嗪-3-羧酸S-氧化物(9)和(–)亚砜(7b)产生相应的赤道亚砜(10 R)。这将无环亚砜(7a和b)的绝对构型确定为R和S分别在硫磺下。将环状亚砜还原为相应的环状硫化物,然后将该化合物再氧化,仅得到赤道亚砜(10),这表明轴向甲基的空间位阻很大。环构象和亚砜构型的分配基于光谱证据。