The bacterial pigment from Pseudomonas lemonnieri. Part 1. Structure of a degradation product, 3-n-octanamidopyridine-2,5,6-trione, by X-ray crystallography

Abstract

Degradation with chromic acid of the blue pigment, lemonnierin, C₂₆H₃₇N₅O₆, from Pseudomonas lemonnieri, gives 3-n-octanamidopyridine-2,5,6-trione (1; R = H), the structure of which has been defined by X-ray analysis of the N-p-iodobenzyl derivative (1; R =p-iodobenzyl). Crystals are orthorhombic, space group Pbca with eight molecules of C₂₀H₂₃IN₂O₄ in a unit cell of dimensions a= 8.68(3), b= 38.71 (5), c= 12.53(3)Å. Intensity data were obtained by visual estimation of Weissenberg films. The structure was solved by the heavy-atom method and refined by block-diagonal least-squares calculations : R= 0.122 for 1 004 measured reflections.

Degradation of (1; R = H) with alkali gives successively (±)-n-octanamidosuccinimide (2) and (±)-n-octanoylasparagine (4), which have been synthesised.

The formal synthesis of (1; R = H) is recorded.