New total synthesis of (+)-cystothiazole A

Palladium-catalyzed cyclization–methoxycarbonylation of (2R,3S)-3-methylpenta-4-yne-1,2-diol (7) derived from (2R,3S)-epoxy butanoate 8 followed by methylation gave the tetrahydro-2-furylidene acetate (−)-9, which was converted to the left-half aldehyde (+)-4. A Wittig reaction between (+)-4 and the phosphoranylide derived from the bithiazole-type phosphonium iodide 5 using lithium bis(trimethylsilyl)amide afforded the (+)-cystothiazole A (2).