Stereochemical studies on the proposed spiro intermediate for the biosynthesis of the natural porphyrins: determination by a novel X-ray method of the absolute configuration of the spirolactam which inhibits cosynthetase

A novel X-ray analysis, combined with correlations by circular dichroism, has been used to establish the (R)-configuration at the stereocentre in that enantiomer of the spirolactam 4 which strongly inhibits uroporphyrinogen III synthase.