ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
An X-ray diffraction analysts of two N-acyl derivatives of symmetrical dialkylureas, N-[Nα-(benzyloxycarbonyl)-L-valyl] -N, N′-diisopropylurea (1) and N-{Nα(tert-butyloxy)carbonyl -L-valyl}-N-N′-dicyclohexylurea (2), and one N-acyl derivative of an unsymmetrical N-N′-dialkylurea, N-[Nα-(benzyloxycarbonyl)-L-valyl] -N′-(tert-butyl)-N-ethylurea (3), has been performed. It was established that it is the least hindered O-acylisourca N-atom that attacks intramolecularly the carbonyl group of the Nα-protected amino acid activated by the unsymmetrical carbodiimide to form the major rearrangement product. The occurrence and nature of intra- and intermolecularly H—bonded forms of the N-acylureas in the crystal state were also assessed. It was also shown that soluble N-acylureas may compete with intermolecular (peptide)N—H…O=C(peptide) H-bonds in CH2Cl2.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19900730311
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