Pyridine-idnduced dishielding of 4-methylene protons for the determination of C-6 stereochemistry of sterols having a 5.ALPHA.,6-diol moiety. Revision of the C-6 stereochemistry of marine sterol isolated from a sponge, Dysidea sp.
作者:YOSHINORI FUJIMOTO、TAKETOSHI YAMADA、NOBUO IKEKAWA
DOI:10.1248/cpb.33.3129
日期:——
The utility of the proton nuclear magnetic resonance method involving pyridine-induced deshielding was demonstrated for stereochemical assignment at the C-6 position of sterols having a 5α, 6ζ-diol moiety. Thus, the 4α-hydrogen resonance of 6α-isomers such as cholest-7-ene-3β, 5α, 6α-triol (8) is observed at ca. 3.0 ppm, whereas the 4β-hydrogen resonance of 6β-isomers such as cholest-7-ene-3β, 5α, 6β-triol (10) is observed at ca. 3.0 ppm. This method was applied to a marine sterol (4) isolated from a sponge, Dysidea sp., and it was concluded that the structure should be revised to the 6α-isomer (5) rather than the reported 6β-isomer (4).
通过吡啶诱导去屏蔽的质子核磁共振方法,展示了在具有5α, 6β-二醇基团的甾醇C-6位的立体化学分配中的应用。因此,像胆甾-7-烯-3β, 5α, 6α-三醇(8)这样的6α-异构体的4α-氢共振在大约3.0 ppm处被观察到,而像胆甾-7-烯-3β, 5α, 6β-三醇(10)这样的6β-异构体的4β-氢共振同样在大约3.0 ppm处被观察到。该方法被应用于从海绵Dysidea sp.分离出的海洋甾醇(4),并得出结论,结构应修订为6α-异构体(5),而非报告的6β-异构体(4)。