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The syntheses of aureobasidin A (AbA) derivatives with alkyl chains and their in vitro structure-biological activity relationships are discussed. The analogs replaced at positions 6, 7, or 8 of AbA with either L-glutamic acid, delta-hydroxy-L-norvaline, or delta-hydroxy-N-methyl-L-norvaline are prepared. The gamma-carboxyl or delta-hydroxyl group of these new amino acids was coupled with acids, alcohols, or amines with alkyl chains. While the analogs having L-glutamic acid residue at positions 6 or 8 showed weak activity, esterification of the gamma-carboxyl group with benzyl or shorter alkyl (C4 or C6) alcohols, significantly enhanced the activities. Introduction of longer alkyl (C14) chain to the same amino acids residues at positions 6, 7, or 8 resulted in total loss of antifungal activity. Among the lipophilic analogs in [L-Glu6] derivatives, the C6 alcohol ester showed the strongest antifungal activity against Candida spp. so far tested. None of the derivatives showed activity against Cryptococcus neoformans.

A new inhibitor of angiotensin I converting enzyme, I5B2, was isolated from the culture broth of Actinomadura sp. No. 937ZE-1. This compound contains N-methylvaline, tyrosine and 1-amino-2-(4-hydroxyphenyl)ethylphosphonic acid. The microorganism also produced another inhibitor, I5B1, which is identical with K-4 isolated from Actinomadura sp. as an antihypertensive agent.

The total structures of capreomycins IA and IB were determined mainly from the results of the comparative study on the NMR spectra of capreomycins and tuberactinomycins, resulting in a revision of the formerly proposed structure. The beta-lysine residue as a branched part was revealed to be linked with the beta-amino group of the alpha, beta-diaminopropionic acid residue in the cyclic pentapeptide moiety in a different manner than in tuberactinomycins.

Palmitoyltuberactinamine N (Pal-Tua N) and di-beta-lysylcapreomycin IIA (di-beta-Lys-Cpm IIA), which are synthetic derivatives of the antituberculous agent tuberactinomycin (Tum) and capreomycin (Cpm) respectively, were tested for anti-bacterial activity. Pal-Tua N inhibited not only tuberactinomycin-resistant Mycobacterium smegmatis but also Escherichia coli, Corynebacterium diphtheriae, Staphylococcus aureus, Streptococcus pyogenes, although it has lost activity against Mycobacterium tuberculosis. Di-beta-Lys-Cpm IIA inhibited the growth of laboratory-derived Tum-resistant M. smegmatis and M. tuberculosis as well as Tum-resistant M. tuberculosis from patients with one exceptional case.

Tuberactinomycin O, one of the four congeners of the antituberculous peptide tuberactinomycin, was totally synthesized. The β-ureidodehydroalanine moiety was constructed from β, β-diethoxyalanine with excess urea in acidic medium after a cyclization reaction of a pentapeptide was finished. Cyclization was carried out by means of the 1-succinimidyl ester method. To the cyclic pentapeptide, β-lysine was introduced as the branched moiety and then deprotected to afford tuberactinomycin O which was completely identified with the natural form of the antibiotic.