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Conformational response of tartaric acid to derivatization: Role of 1,3‐dipole–dipole interactions
Author(s) -
Gawronski Jacek,
Długokinska Anna,
Grajewski Jakub,
Plutecka Agnieszka,
Rychlewska Urszula
Publication year - 2005
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.20181
Subject(s) - conformational isomerism , chemistry , tartaric acid , alkane stereochemistry , antiparallel (mathematics) , crystallography , gauche effect , dipole , chirality (physics) , stereochemistry , molecule , organic chemistry , crystal structure , quantum mechanics , magnetic field , citric acid , medicine , physics , surgery , nambu–jona lasinio model , chiral symmetry breaking , quark
The four‐carbon chain in ( R,R )‐tartaric acid derivatives is predominantly antiperiplanar ( trans ) in the acid, its salts, esters, and NH‐amides, while (−)‐synclinal ( gauche ) conformer is the most abundant in N,N ′‐tetraalkyltartramides. Trialkylsilylation or tert ‐butylation of the hydroxy groups at C2 and C3 does not appear to affect the conformational preference of NH‐tartramides, but it does change the conformational equilibrium in the case of tartrates (toward (−)‐ gauche ) and N,N ′‐tetraalkyltartramides (toward trans ), as judged from the NMR data. X‐ray diffraction data point to the stabilizing role of antiparallel dipole–dipole interactions due to the 1,3‐CO/CH bonds. These interactions can be found in the trans and (−)‐ gauche conformers but are not possible for the (+)‐ gauche conformers of ( R,R )‐tartaric acid derivatives. This rationalizes small proportion of (+)‐ gauche conformers in tartaric acid derivatives and points to a significance of 1,3‐dipole–dipole interactions. The conformation around the C1–C2 (and C3–C4) bond is different in tartrates (O–C–C=O, syn ) and tartramides (O–C–C=O, anti ); the CD data ( n –π* band) show that O–silylation or O – tert ‐butylation brings about conformational changes around the C1–C2 bond in the case of N,N ′‐tetraalkyldiamides only. Chirality 17:388–395, 2005. © 2005 Wiley‐Liss, Inc.