Crystal structures of two isomorphous solvates of the macrolide antibiotic borrelidin [ borrelidin 3-methylbutan-1-ol (A) and borrelidin (S)-2-methylbutan-1-ol (B)] have been determined from X-ray diffractometer data recorded at 294 and 152 K respectively. Crystals are monoclinic, space group P21, with a 13.501(2), b 12.000(2), c 11.863(2) � , β 110.76(1)� [(A); T = 294 K], and a 13.565(2), b 11.646(2), c 11 .376(3) �, β 109.76(1)� [(B); T = 152 K], (Z = 2). The structures were solved by direct-methods procedures and refined by full-matrix least-squares analysis to conventional R-factors of 0.061 [(A), 2676 reflections] and 0.048 [(B), 2851 reflections]. The absolute configuration of borrelidin follows from the known chirality of the (S)-2-methylbutan-1-ol solvent in (B), and is 3S,4S,6S,8R,1OS,11R,17S,18R,22R. The unusual structural and stereochemical features of borrelidin are discussed in relation to other macrolide antibiotics.

The antibiotic responsible for the high antiyeast and antifungal activity of a streptomycete fermentation is shown to be the 9-methyl derivative (1) of streptimidone (2). The conjugated diene system in (1) is assigned the 6E,8Z stereochemistry. Evidence is presented for the biogenetic origin of the 9-methyl group in this streptimidone homologue, and its antifungal activity is compared with that of streptimidone and other fungicides.

Hodge and Rickards. The Halogenation of Methyl Pyrrole-2-carboxylate and ofSome Related Pyrroles.

Efficient syntheses are reported of the natural amino acid 3-amino-5-hydroxybenzoic acid in unlabelled and carboxyl-labelled forms from 3,5-dinitrobenzoic acid and 3,5-dinitroanisole, respectively.

Aspergillus indicus grown on a semi-synthetic medium produces a number of metabolites including kojic acid, succinic acid, fumaric acid, β-nitropropionic acid, indazonic acids, fumaryl-~danine, and dihydrocanadensolide. The last compound is shown to have the formula (I) and is biosynthesized in part from "acetate" units; the rest of the molecule may come from pyruvic acid.