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Phytochemical investigation of the stem bark extract of Psychotria djumaensis led to the isolation of ten known pentacyclic triterpenoids among which one lupane-, three oleanane-, and six ursanetypes. The structures of the isolated compounds were established by means of spectroscopic methods and by comparison with previously reported data. The isolated compounds were tested against five strains of bacteria, and the cytotoxicity against the human cervix carcinoma KB-3-1 cell was evaluated. The isolates exhibited weak antibacterial activity against the five strains. The cytotoxic activity exhibited by 3ß,19a-dihydroxyurs-12-en-28-oic acid (5) (IC50 5.9 µM) was about three times more significant than that of the reference [(+) griseofulvin, IC50 17-21 µM]. [ABSTRACT FROM AUTHOR]

Covering: 1995 to December 2007 [ABSTRACT FROM AUTHOR]

Five suitably protected enantiomerically pure 2-amino acids, homologues of proteinogenic a-amino acids, were synthesized from the common chiral precursor, tert-butyl succinyloxazolidinone. [ABSTRACT FROM AUTHOR]

a-Azido carboxylic acids have recently emerged as versatile N-protected equivalents for a-amino acids, especially valuable when the sterically hindered Ca-dialkylated a-amino acids have to be incorporated. Unsymmetrically substituted Ca-dialkylated a-azido carboxylic acids can be obtained in enantiomerically pure form by enzymatic resolution of a-azido carboxamides. A l-amidase from Ochrobactrum anthropi NCIMB 40321 accepts 2-azido-2,4-dimethylpentanamide as the substrate and provides both the corresponding S-configured a-azido carboxylic acid and the R-configured a-azido carboxamide in excellent enantiomeric purity. The former is a valuable synthetic precursor of a-methylleucine [(a-Me)Leu] in peptide synthesis, as demonstrated by the successful synthesis of a (a-Me)Leu containing efrapeptin C analogue. [ABSTRACT FROM AUTHOR]