Compounds of formula (I): ##STR1## (wherein R represents a group of formula ##STR2## and the corresponding ring-closed lactones, salts (especially alkali metal salts) and esters (especially C.sub.1 -C.sub.5 alkyl esters) thereof may be prepared by subjecting ML-236B, or ML-236B carboxylic acid or a salt...http://www.google.co.uk/patents/US4346227?utm_source=gb-gplus-sharePatent US4346227 - ML-236B Derivatives and their preparation
