Lewis acid catalysis of photochemical reactions. 5. Selective isomerization of conjugated butenoic and dienoic esters
作者:Frederick D. Lewis、Daniel K. Howard、Steven V. Barancyk、Joe D. Oxman
DOI:10.1021/ja00271a034
日期:1986.5
nonselective E,Z isomerization to give mixtures of all four stereoisomers in roughly comparable yields. In the presence of the Broensted acid trifluoroacetic acid, quantitative conversion of methyl 2,4-hexadienoates to methyl 3,4-hexadienoate is observed. The acid serves as a catalyst for the thermal 1,3-hydrogen shift of an allenic enol ester formed via a photochemical 1,5-hydrogen shift of the conjugated
The structure of the steroidallactone (previously designated as tetrahydroxysterocholanic acid lactone) isolatedfrom the bile of Amyda japonica(turtle) has been characterized as (22S,25R)-3α,7α,12α-trihydroxy-5β-cholestano-26,22-lactone (1). The 22S,25R configuration was determined by 1H n.m.r. comparison with the reference compounds, four possible stereoisomers (with respect to the C-22 and C-25
从Amyda japonica(乌龟)的胆汁中分离的甾体内酯(以前称为四羟基硬脂酸内酯)的结构特征为(22 S,25 R)-3α,7α,12α-三羟基-5β-cholestano-26, 22-内酯(1)。通过1 H nmr与参考化合物,6β-甲氧基-3α,5-环-5α-胆甾醇的四种可能的立体异构体(相对于C-22和C-25位置)比较,确定22 S,25 R构型-26,22-内酯(7)–(10)。
Plisow; Paladienko, Zhurnal Obshchei Khimii, 1958, vol. 28, p. 503,503, 505; engl. Ausg. S. 494, 496
作者:Plisow、Paladienko
DOI:——
日期:——
v.Auwers, Justus Liebigs Annalen der Chemie, 1923, vol. 432, p. 65