N-Acylpeptides with a Linear Peptide Moiety

By heating majusculamide B in dimethylsulfoxide at 140°C for 15 hours, 2-methyl-3-oxodecanoic amide (26) and the diketopiperazine formed from N,0-dimethyl-tyrosyl-N-methylvaline (27) were obtained. Acid hydrolysis of the majusculamides under mild conditions gave 

From these data, structure (25) was proposed for the majusculamides and was confirmed by X-ray crystallographic studies on the B isomer. Majusculamides A and B are isomers differing only in the stereochemistry of the asymmetric center in position 2 of the keto fatty acid (7/). 

R—COOH = normal chain fatty acids C20-C28 or mycolic acids C28-C42 

Hydrolysis of the polar peptidolipids which consisted of four components gave glycine, L-leucine, D-a//oisoleucine, L-threonine, L-serine, l-homoserine and o-alanine in the molar ratio 3 3 2 2 2 1 1. Two of these compounds contained glucose bound to the hydroxyl group of serine or threonine and thus were glucosides of peptidolipids all of them contained mycolic acids 74). Their complete structures have not yet been established. 

From a lipid extract of Mycobacterium paratuberculosis a peptido-lipid fraction was isolated thanks to its insolubility in ether. Chemical analysis showed the presence of the amino acids D-phenylalanine, l-phenylalanine, L-leucine, L-isoleucine and the presence of a methyl ester group at the C-terminal end of the peptide moiety. Presence of an N-acyltetrapeptide was suggested (75). However, mass spectrometric invest- 

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