Dysithiazolamide

A study of a Philippines Dysidea sp. has yielded the novel proline analogs of dysidenin, dysideaprolines A-F (950-955) and barbaleucamides A (956) and B (957), which are reminiscent of barbamide (995). Also from the Philippines was isolated the novel pyrrolidone 958 from the nudibranch Asteronotus cespitosus (996), which is the first example of a Dysidea-type polychlorinated metabolite found in a carnivorous mollusc. An Indonesian collection of Dysidea sp. has furnished dysithiazolamide (959), having the suggested absolute configuration shown (997). 

Dysamide B 293 and dysithiazolamide 295 bear a dichlor-omethyl unit in their molecular architectures. Willis and coworkers have reported on the first enantiospecific synthesis of dysamide B 293, which features a radical method to construct the gew-dichloromethyl motif (Scheme 43.48). Successive treatment of aldehyde 305 with NCS/t-BuNH2 followed by Pinnick oxidation afforded a,a-dichloro carboxylic acid 306. Acid 306 that was reacted with Pb(OAcVl,4-cyclohexadiene underwent radical decarboxylation to provide dichloride 308. This process is likely to involve the intervention of carbon radical 307, which subsequently abstracts hydrogen from 1,4-cyclohexadiene, an excellent... 

SCHEME 43.49. Rodriguez et al. s enantiospecific total synthesis of (—)-dysithiazolamide 295. 

Arda, A., Rodriguez, J., Nieto, R.M., Bassarello. C., Gomez-Paloma, L., Bifuco, G., and Jimenez, C. (2005) NMR J-based analysis of nitrogen-containing moieties and application to dysithiazolamide, a new polychlorinated dipeptide from Dgsidea sp. Tetrahedron. 61, 10093-10098. 

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