CONFORMATION OF CYCLO-(L-THREONINE)2 AND CYCLO-(L-ALLOTHREONINE)2 - A PROTON AND CARBON NMR-STUDY
- 1 January 1981
- journal article
- research article
- Vol. 18 (1) , 33-40
Abstract
The diketopiperazines cyclo-(L-Thr[threonine])2 and cyclo-(L-alloThr)2 in water and in dimethyl sulfoxide were studied by proton and carbon-13 NMR resonance, and the dominant conformations were deduced from proton-proton and proton-carbon coupling constants. In cyclo-(L-Thr)2 the .chi.1 = 60.degree., hydroxyl over the ring, side chain conformation is favored; this conformation is also favored for cyclo-(L-Ser)2 and cyclo-(L-Ser-D-Ser). The important side chain conformation for cyclo-(L-alloThr)2 is .chi.1 = -60.degree., methyl group over the diketopiperazine ring. The determining factors are apparently steric. The diketopiperazine ring of cyclo-(L-Thr)2 is puckered to hold the side chains more nearly axial than is that of cyclo-(L-alloThr)2, although the degree of ring folding is probably not large.This publication has 9 references indexed in Scilit:
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