NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, CARBON-13 SPECTRA OF CHOLIC ACIDS AND HYDROCARBONS INCLUDED IN SODIUM DESOXYCHOLATE SOLUTIONS
NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, CARBON-13 SPECTRA OF CHOLIC ACIDS AND HYDROCARBONS INCLUDED IN SODIUM DESOXYCHOLATE SOLUTIONS
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核磁共振波谱、去氧胆酸钠溶液中胆酸和碳氢化合物的碳 13 波谱
DOI：
10.1002/chin.197339082
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发表时间：
1973
期刊：
影响因子：
--
通讯作者：
John D. Roberts
中科院分区：
文献类型：
--
作者：
D. Leibfritz;John D. Roberts
记录了胆酸、去氧胆酸、鹅去氧胆酸和石胆酸及其衍生物的13C共振，并将其与特定的碳原子进行了对应。比较顺式和反式A/B环连接类固醇的碳化学位移，发现C环和D环上的原子有很大的相似性，但A环和B环上的一些原子有很大的差异。通过比较碳核的7j弛豫时间和使用镧系移位试剂充分分离碳共振以简化非共振、部分质子解耦光谱的解释，使分配任务更加容易。D20溶液中的去氧胆酸钠除了甲基碳和季碳外，对所有碳都有相当广泛的碳共振，正如预期的那样，存在大量的分子间缔合。这些溶液以2:1的摩尔比吸收对二甲苯和2-甲基萘。所含物质的13C光谱表明，2-甲基萘的分子运动有相当大的限制，而对二甲苯的分子运动相对较少。利用脉冲射频功率和傅立叶变换分析自由感应衰减光谱的核磁共振光谱仪最近的快速发展，使得在相当短的时间内，在低浓度下，甚至是非常复杂的天然产物的13C磁共振（cmr）光谱的自然丰度水平得以测定。然而，获得这种化合物的cmr光谱和解释它并不是完全一样的事情。类固醇呈现出一个特别困难的问题，因为它们的许多共振落在一个相当窄的移位范围内。早期对全反式类固醇的研究，由于有大量的替代产物，使其具有合理的as-
The 13C resonances of cholic, desoxycholic, chenodesoxycholic, and lithocholic acids and some of their derivatives have been recorded and assigned to specific carbons. Comparison of the carbon chemical shifts for steroids with cis and trans A/B ring junctions show substantial similarities for the atoms in the C and D rings but large differences for some of the atoms in the A andB rings. The task of making the assignments was facilitated by comparisons of the 7j relaxation times of the carbon nuclei and the use of lanthanide shift reagents to separate the carbon resonances sufficiently to simplify the interpretation of the off-resonance, partially proton-decoupled, spectra. Sodium desoxycholate in D20 solution gives rather broad carbon resonances for all but the methyl and the quaternary carbons, as expected for substantial intermolecular association. These solutions take up p-xylene and 2-methylnaphthalene in about 2: 1 molar ratios. The 13C spectra of the substances so included indicate that there is considerable restriction of the molecular motion of the 2-methylnaphthalene, but relatively little of p-xylene.The recent rapid development of nmr spectrometers using pulsed rf power and Fourier transform analy-sis of free-induction decay spectra has permitted taking the 13C magnetic resonance(cmr) spectraat natural-abundance levels of even quite complex natural prod-ucts at low concentrations in rather short times. However, obtaining a cmr spectrum of such com-pounds and interpretingit are not quite the same thing. The steroids present an especially difficult problem be-cause many of their resonances fall in a fairly narrow shift range. An early study of all-trans steroids-was greatly facilitated bythe plethora of available sub-stitution products which permitted reasonable as-