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8 páginas, 4 figuras, 4 tablas, 3 schemes.The R*,R* and R*,S* diastereomers of N,N'-diacetyl-N,N'-dimethyl-l,2-diamino-\ud1,2-diphenylethane and their mono- and di-thio analogues (1-6) have been\udstudied by 1H and 13C NMR spectroscopy and by empirical force-field calculations\ud(MMP2-85). The NMR spectral data (chemical shifts, coupling constants and NOE)\udclearly show that al1 compounds exist in the anti conformation with the Z,Z configuration\udfor the (thio)amide groups. The same result is obtained by the force-field\udcalculations.\udFour of the compounds (2, 3, 4 and 6) are chiral and have been resolved into\udenantiomers by chromatography on triacetylcellulose. The CD spectra of the first\udeluted enantiomers of 4 and 6 could be reasonably well reproduced by calculations\udbased on minimum energy geometries for the S,S enantiomers, whereas no agreement\udcould be reached for 2 and 3. This agrees with the results of the force-field\udcalculations, which predict one predominant conformer for each of 4 and 6 , but\udsignificant amounts of two rotamers (both anti ZZ) for each of 2 and 3.The work described here is part of a\udproject supported by the Bulgarian and the Swedish Academy\udof Sciences. The authors acknowledge financia1 support\udby the Academies and by the Swedish Natural Science\udResearch Council, in particular for a guest professorship\udfor S. L. S., and by the Knut and Alice Wallenberg Foundation.Peer reviewe

acta chemica scandinavica/acta chemica scandinavica. b, organic chemistry and biochemistry/acta chemica scandinavica. a, physical and inorganic chemistry/acta chemica scandinavica. series b. organic chemistry and biochemistry/acta chemica scandinavica. series a, physical and inorganic chemistry

Stereochemical Studies of N,N'-Diacetyl-N,N'-dimethyl-1,2-diamino-1,2-diphenylethanes and their Mono- and Di-thio Analogues by NMR and CD Spectroscopy and by Molecular Mechanics Calculations.