Herein we report radical trapping experiments that support the formation of an acyl radical as the active species from the oxidation of isoniazid; these data provide insight into the mechanism of hydrazide oxidation.

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Abstract-An investigation of the reaction requirements to effect the Clauson-Kaas pyrrole synthesis led to the formulation of a new procedure that avoids the contact of pyrroles to heat or strongly acidic conditions that cause decomposition of the desired products. The procedure involves mild hydrolysis of 2,5-dimethoxytetrahydrofuran in water to the activated species 2,5-dihydroxytetrahydrofuran that reacts with primary amines in an acetate buffer at room temperature to give N-substituted pyrroles in high yield. In the case of chiral amines, pyrrole formation proceeds with no detectable epimerisation. Acid-or heat-sensitive pyrroles are also obtained in high yield and purity.

Aryl hydrazides are oxidised to acyl radicals through a mechanism involving diimide intermediates that are prone to nucleophilic acyl substitution. This oxidation occurs regardless of the oxidant involved, however there is no evidence that the acyl radical formed undergoes further oxidation to the corresponding acylium ion, even in the presence of strong oxidants. This study may provide insight into the mechanism of isoniazid resistance in Mycobacterium tuberculosis.

Alkaloids U 0600 Annulation of Pyrrole: Application to the Synthesis of Indolizidine Alkaloids. -Key step of the synthesis of various indolizidine alkaloids is the annulation of the piperidinone ring onto pyrrole (I) by nucleophilic substitution and subsequent ring closure. The synthesis of alkaloid (±)-monomorine (XII) is presented. -(AMOS, R. I. J.; GOURLAY, B. S.; MOLESWORTH, P. P.; SMITH*, J. A.; SPROD, O. R.; Tetrahedron 61 (2005) 34, 8226-8230; Dep. Chem., Univ. Tasmania, Hobart, Tasmania 7001, Australia; Eng.) -Mischke 49-178

Background

Abstract-An investigation of the reaction requirements to effect the Clauson-Kaas pyrrole synthesis led to the formulation of a new procedure that avoids the contact of pyrroles to heat or strongly acidic conditions that cause decomposition of the desired products. The procedure involves mild hydrolysis of 2,5-dimethoxytetrahydrofuran in water to the activated species 2,5-dihydroxytetrahydrofuran that reacts with primary amines in an acetate buffer at room temperature to give N-substituted pyrroles in high yield. In the case of chiral amines, pyrrole formation proceeds with no detectable epimerisation. Acid-or heat-sensitive pyrroles are also obtained in high yield and purity.

The structural assignments of a number of bicyclic alkaloids isolated from frogs have been reassigned or questioned after synthesis of the proposed structures. Herein we report a practical and short formal synthesis of the 5-alkylindolizidine core, from readily available α-amino acids or homoserine that could be utilized to support structural assignments.