CHEMISTRY AND ANTIMICROBIAL ACTIVITY OF CARYOYNENCINS ANALOGS

Caryoynencins (1) are antibiotics isolated from liquid cultures of a p lant pathogen, Pseudomonas caryophylli, and are unstable C-18 carboxyl ic acids with a conjugated dienetetrayne structure. Enyne analogs of c aryoynencins were synthesized from monosilylated 1,3-butadiyne 2 (n = 2), 1,3,5-hexatriyne 2 (n = 3), and 1,3,5,7-octatetrayne 2 (n = 4) by alkynyl metal addition to 2,4-hexadienal (3) followed by allylic rearr angement and deprotection. Tetraynol 5 (n = 4) thus obtained was resol ved by enzyme reactions. The conjugated dienetetrayne compounds are mi xtures of 3E,5E- and 3E,5Z-isomers, which equilibrate by room light. C -13-NMR chemical shifts of polyynes obey simple rules, which can be us ed for signal assignments. Antimicrobial activities of conjugated enyn es and related compounds were examined. The tetrayne analog 6 (n = 4) possesses potent antibacterial and antifungal activities, while triyne and diyne analogs 6 (n = 3 and 2) are less active. Chirality does not affect the activities. An isomeric enyne compound, 2,4-tetradecadiene -7,9,11,13-tetrayn-6-ol (8), showed potent activity against Tricophyto n.