Total synthesis of prodigiosin, prodigiosene, and desmethoxyprodigiosin: Diels-Alder reactions of heterocyclic azadienes and development of an effective palladium(II)-promoted 2,2'-bipyrrole coupling procedure
作者:Werner Hinz、R. Alan Jones、Sunil U. Patel、(in part) Mary-Helen Karatza
DOI:10.1016/s0040-4020(01)87527-x
日期:1986.1
Nucleophilic addition to but-1-en-3-one by the acyl anion equivalent of 2-formylpyrroles, generated by reaction with thiazolium salts, yields 1-(2-pyrrolyl)pent-1,4-diones, which undergo the Paal-Knorr reaction with ammonia and primary amines to give the 2,2'-bipyrroles. Alternatively, the 2,2'-bipyrrole system can be obtained by pyrolysis of 2-azido-5-(2-pyrrolyl)penta-2,4-dienoic esters.
The total synthesis of prodigiosin (1), possessing the characteristic pyrrolylpyrromethene skeleton of a class of naturally-occurring polypyrroles, is detailed, The approach is based on the application of an inverse electron demand Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate in a 1,2,4,5-teirazine → 1,2-diazine → pyrrole strategy for preparation of prodigiosin pyrrole ring