Conformational studies of D-glycals by 1H nuclear magnetic resonance spectroscopy
- 1 January 1974
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 728-732
- https://doi.org/10.1039/p29740000728
Abstract
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.Keywords
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