The synthesis of the macrolide antibiotic (+/-)-pyrenophorin (1) is described. The molecular sieve promoted cyclisation of the hydroxy methyl ester (135) failed in our hands but the hydroxy-acid (190) was successfully converted to the dithioacetal of (1) using N,N'-carbonyldiimidazole (207) and 1,5-diazabicyclo(4,3,0)-non-5-ene (147). A novel method of removing p-toluenesulphonylethyl esters (166) is reported as is a new simple technique of hydroxyl alkyl-ation involving molecular sieves and sodium hydrogen carbonate
