Two new enantioselectivesyntheses of the naphthopyranquinone antibiotic frenolicin B (1), of its enantiomer 2, and of its diastereoisomers 3 and 4 were accomplished using two different routes from optically active β-Hydroxy esters (R)- and (S)-11 and 18. β-Hydroxy esters (R)- and (S)-11 were prepared stereoselectivelyfrom optically active sulfenylacetates (S)- and (R)-10, respectively (Scheme 2,
Starting from juglone derivative 5, a series of frenolicin B analogs 15 (R1 = R2 = Me), 19a (R1 = H, R2 = Ph), and 19b (R1 = Ph, R2 = H) were obtained via the key β-hydroxy ester intermediate 10 in a twelve step synthesis.