A simple, modular synthesis of C4-substituted tryptophan derivatives.

The modular and versatile synthesis of C4-substituted tryptophan derivatives by direct functionalization of easily available N-acetyl 4-boronate tryptophan methyl ester via transition metal-catalyzed and metal-mediated cross coupling reactions is described. The versatility of the chemistry is highlighted by the gram-scale synthesis of 4-boronated N-acetyl-tryptophan methyl ester and the rapid synthesis of C4-aryl, C4-alkyl, C4-cyano, C4-trifluoromethyl, C4-azido, and C4-hydroxy tryptophan derivatives. The utility of our methodology is illustrated through the quick approach to the tricyclic azepino indole skeleton embedded in many natural products.

Synthesis of new C-6 alkyliden penicillin derivatives as beta-lactamase inhibitors.

New penicillin, penicillin sulfone and sulfoxide derivatives bearing a C-6-alkyliden substituent were prepared. Their chemical synthesis, in vitro antibacterial activity and inhibition properties against two selected enzymes representing Class A and C beta-lactamases are reported. Compounds 3a-c, 7a-c were able to inhibit either TEM-1 (a Class A enzyme, from Escherichia coli) or P-99 (a Class C enzyme, from E. cloacae), or both enzymes, when tested in competition experiments using nitrocefin as the reporter substrate. However, when tested in combination with amoxicillin, the same compounds did not show synergistic effects against E. coli and E. cloacae strains producing TEM-1 and P99 enzymes, respectively. This finding is most likely related to poor penetration through the bacterial cell wall, as shown by using a more permeable isogenic E. coli strain. Interestingly, a synergistic effect against a strain of S. aureus which produces PC1-enzyme (a Class A beta-lactamase) was observed for compound 3a when used in combination with amoxicillin.