CONFORMATIONAL STUDIES OF D-GLYCALS BY H-1 NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY
CONFORMATIONAL STUDIES OF D-GLYCALS BY H-1 NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY
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DOI：
10.1039/p29740000728
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发表时间：
1974-01-01
期刊：
影响因子：
--
通讯作者：
HALL, RH
中科院分区：
文献类型：
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作者：
CHALMERS, AA;HALL, RH
如1H n.m.r所示，完全O-乙酰化D-糖醛(和相关化合物)的首选半椅子构象。光谱分析表明，耦合常数4J2，4对构象变化最为敏感。除了二-O-乙酰基-D-木醛采用替代的5H4(D)构象外，所有六个完全O-乙酰化-D-糖基在溶液中都有利于4H5(D)构象。这些构象偏好可以通过考虑C(3)、C(4)和C(5)上取代基之间的相互作用和‘烯丙基效应’来合理化。通过在葡萄糖和半乳糖醛中引入C(2)上的取代基，可以发生环扁平或5H4构象的反转以缓解应变。
The preferred half-chair conformations of the fully O-acetylated D-glycals (and related compounds), as indicated by 1H n.m.r. spectroscopy, show that the coupling constant 4J2,4 is the most sensitive to conformational change. All six fully O-acetylated-D-glycals favour the 4H5(D) conformation in solution, except di-O-acetyl-D-xylal which adopts the alternative 5H4(D) conformation. These conformational preferences can be rationalised by considering the interactions between the substituents at C(3), C(4), and C(5) and the ‘allylic effect’. With the introduction of a substituent at C(2) in glucals and galactals, ring-flattening or inversion to the 5H4 conformation can take place to relieve strain.