Anders K. Petersen

Pyrrole-singlet oxygen reactions leading to α,α′-bipyrroles. Synthesis of prodigiosin and analogs

Abstract Reaction of the tert -butyl ester of 3-methoxy-2-pyrrolecarboxylic acid with singlet oxygen yields a hydroperoxide intermediate which undergoes coupling with pyrroles to yield precursors of prodigiosin and ring A analogs, readily convertible to the corresponding tripyrromethenes.

Synthesis of the peptidic α-hydroxy amides phebestin, probestin, and bestatin from α-keto amide precursors

Abstract Aminopeptidase inhibitors, phebestin, probestin and bestatin have been prepared by stereospecific reduction of α-keto amide precursors using zinc borohydride.

A convergent synthesis of poststatin: Application of the acyl cyanophosphorane coupling procedure in the formation of a peptidic α-keto amide

Abstract A convergent synthesis of the pentapeptide poststatin has been developed. The key step involves oxidative cleavage of an acyl cyanophosphorane. The resulting α,β-diketo nitrile is then coupled to the free amine of a C -terminal-dipeptidyl component to generate the protected natural product. Deprotection by hydrogenolysis furnishes poststatin.

Application of acyl cyanophosphorane methodology to the synthesis of protease inhibitors: poststatin, eurystatin, phebestin, probestin and bestatin

Full details are given for the syntheses of the protease inhibitors, poststatin and eurystatin by the acyl cyanophosphorane coupling procedure used for the formation of α-keto amides. We have also extended this methodology to the syntheses of the related α-hydroxy amide natural products, phebestin, probestin and bestatin. The key step in the latter synthetic sequences involved diastereomeric selectivity in the reduction of the α-keto precursor to the corresponding α-hydroxy amide by the use of zinc borohydride.

Singlet oxygen oxidation of pyrroles. Formation of 5-substituted derivatives

Abstract The tert -butyl ester of 3-methoxy-2-pyrrolecarboxylic acid 3 undergoes reaction with singlet oxygen to form an intermediate imino hydroperoxide 4 . This hydroperoxide may be trapped by a variety of nucleophiles yielding 5-substituted pyrroles 6 . With strong nucleophilic substituents at the 5-position, these pyrroles may add to unreacted hydroperoxide 4 to form bipyrrole-like products 7 .

TANDEM CYCLOPROPYLCARBINYL/OXIRANYLCARBINYL RADICAL REARRANGEMENTS : AN ENTRY INTO THE PROSTAGLANDIN B1 SERIES

Abstract A tandem radical fragmentation of a cyclopropylcarbinyl/oxiranylcarbinyl system leads to the PGB 1 series of prostaglandins. Control of cyclopropane bond fragmentation as a function of C 2 substitution in bicyclo[3.1.0]hexanylcarbinyl radicals is presented.

Pyrrole photooxidation. A pathway to bipyrrolic products

Dye-sensitized photooxidation of tert-butyl 3-methoxypyrrole-2-carboxylate in methanol yielded tert-butyl 3,5-dimethoxypyrrole-2-carboxylate and a bipyrrolic oxidative coupling product. A mechanism for the formation of the coupling product is presented.