Sc. Mayer et al., THE CYCLIC DEPSIPEPTIDE BACKBONE OF THE DIDEMNINS, Acta crystallographica. Section C, Crystal structure communications, 51, 1995, pp. 1609-1614
An X-ray crystal analysis of phi-lactone ,5-dimethyl-1,3-dioxohexyl}-L
-leucyl}-L-prolyl}-N, O-dimethyl-L-tyrosine hydrobromide hydrate (1a),
C42H66N5O11+.Br-.H2O, was obtained in order to determine the backbone
folding of the macrocycle and to compare the results obtained with th
ose reported previously for the natural product didemnin B (1b). Some
differences were noted in the torsion angles of the two conformers of
the hydrobromide salt, denoted (1a) and (1a'). The conformation of (1a
') resembled the conformation of (1b) more closely than did that of (1
a). Certain regions of both crystal backbones were more flexible than
those in didemnin B; however, the transannular hydrogen bonds in both
(1a) and (1a') were somewhat stronger than in (1b).