Sir:An antibiotic enterocin was obtained from Streptomt7ces candidus var.enterostaticus and S. viridochromogenes var.M-127 which were isolated from soil samples.Fnterocin has static activities against gram-positive and gram-negative bacteria').Chemical and spectroscopic investigations of enterocin accounted for four hydroxyl groups, a 4-methoxy-2-oxo-pyrone and a benzoyl ring, but the structure of the skeleton remained unknown.X-Ray crystallographic analysis of m-bromobenzoyl enterocin dihydrate was therefore undertaken to establish the molecular structure of enterocin.The present study revealed that the major skeleton of enterocin was a unique tricyclic structure containing a y-lactone.m-Bromobenzoyl enterocin was obtained by treating enterocin with m-bromobenzoyl chloride in the presence of pyridine.Crystals suitable for X-ray work were obtained from an ethyl acetateethanol mixture as colorless plates.Unit-cell dimensions were determined by a least-squares calculation using the high-angle reflections of Cuka1 and CuKR2 on zero-layer Weissenberg photographs, on which were superimposed Al wire patterns for calibration.The density was measured by floatation in a benzene-carbon tetrachloride mixture.Crystal data are as follows: C29O11H23Br•2H2O, mp 163-167°C, MW 664.4,orthorhombic, a = 13.61(1),b = 26.61(1),c = 7.73(1)A, D, = 1.55,D° = 1.58g/cros,Z = 4.The systematic absence of the odd orders of the h00, OkO and 001 reflections were observed, hence the space group was found to be P212121.A total of 2,306 non-zero reflections, out of a
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Tokuma et al. (1976) studied this question.