By suitable protection and deprotection, the 9-hydroxynonanoic acid side-chain of pseudomonic acid A (1 a), a naturally occurring antibiotic, was cleaved in a highly efficient one-pot reaction to the allylic acid (3a). 4-[5S-(2S.3S-epoxy-5shydroxy-4s-methylhexyl) -3R.4R-di hydroxytetrahydropyran -2S-ylI -3-methylbut-2 ( E ) -enoic acid. We have ascribed the trivial name, monic acid A, to this allylic acid. Esters of monic acid A were readily prepared from the free acid (3a) and also from the ketone (2) which could be condensed with phosphonoacetates.PSEUDOMONIC ACID A, a naturally occurring antibiotic produced by fermentation of a strain of Pseudomonas fluorescens, was assigned the gross structure (la) by general protein binding appears to correlate with lipoyhilicity one approach to reducing the extent of binding was to attempt the replacement of this C-9 acidic alcohol with shorter chain alcohols. In other words, we sought to effect a transesterification of pseudomonic acid A (la).In our first approach to simple esters of the allylic acid (3a), to which we have given the trivial name monic acid A, we utilised the readily available ketone triol (2). Reaction of (2) with the Wadsworth-Emmons reagent, triethyl phosphonoacetate (4a), in a stirred suspension of sodium hydride in tetrahydrofuran, provided a complex mixture in which both ethyl monate A (3c) and ethyl 1 2 isomonate A (5a) were present as shown by h p.1.c.

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Die hydrolytische Abspaltung der 9‐Hydroxynonansäure‐Seitengruppe von Pseudomonsäure A (Ia) gelingt (ein einem 4‐Schritt‐Eintopfverfahren) nach Schutz der Hydroxygruppen (Bildung des Derivats (Ib) (Reaktion mit Trimethylorthoformiat)) durch alkalische Hydrolyse [→(IIa)], milde Säurebehandlung [ ‐+ (IIb) + (IIc)] und nachfolgende milde alkalische Hydrolyse [→(IId) (Monsäure A)].

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