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Diene chirality and cotton effects of nonhomoannular cisoid conjugated dienes: Circular dichroism and crystal structure of a steroidal 19‐nor‐1(10),9(11)‐diene derived from westphalen's diol diacetate
Author(s) -
Burgstahler Albert W.,
Jahansouz Hossain,
Véliz Eduardo A.,
Takasugawa Fusao
Publication year - 2002
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.10067
Subject(s) - chemistry , diene , chirality (physics) , circular dichroism , conjugated system , diol , cotton effect , conjugated diene , crystal structure , stereochemistry , organic chemistry , chiral symmetry , polymer , natural rubber , physics , quantum mechanics , nambu–jona lasinio model , quark , monomer
Nonhomoannular cisoid conjugated dienes exhibit negative lowest‐energy π→π* Cotton effects when they have P diene chirality and positive CEs when they have M diene chirality. We investigated this relationship further with a variety of such dienes by MM2 conformational energy‐minimization calculations and by an X‐ray crystal structure of a steroidal 19‐nor‐1(10),9(11)‐diene. CEs are stronger when each double bond of the diene is endocyclic in a different ring and weaker when only one of the double bonds is endocyclic or when neither double bond is endocyclic. They are also stronger when axial allylic and homoallylic substituents with CH/π interactions are present that exert consignate chirality contributions. Chirality 14:180–186, 2002. © 2002 Wiley‐Liss, Inc.