(+)-Cystothiazole G: isolation and structural elucidation

Palladium-catalyzed cyclization-methoxycarbonylation of (2 R ,3 S )-3-methylpent-4-yne-1,2-diol ( 6 ) derived from (2 R ,3 S )-epoxybutanoate 5 followed by methylation gave the tetrahydro-2-furylidene acetate (−)- 7 , which was converted to the left-half aldehyde (+)- 3 . A Wittig reaction between (+)- 3 and the phosphoranylide derived from the bithiazole-type phosphonium iodide 4 using lithium bis(trimethylsilyl)amide afforded the (+)-cystothiazole G ( 2 ), whose spectral data were identical with those of the natural product (+)- 2 . Thus, the stereochemistry of cystothiazole G ( 2 ) was proved to be (4 R ,5 S ,6( E )).