Application of Sharpless asymmetric dihydroxylation to thienyl- and benzothienyl acrylates and crotonates

Optimized conditions for the catalytic asymmetric dihydroxylation have been applied to thiophene and benzothiophene containing acrylates and crotonates to afford the corresponding diols in good overall yields and good to excellent enantiomeric excess. The products obtained were revealed to be useful intermediates in peptidomimetic synthesis.

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(2S,3S)-2,3-Dihydroxy-3-(4-phenyl-thiophen-2-yl)-propionic acid ethyl esterC15H16O4SEe = 98%[α]D20=-8.7 (c 0.91, EtOAc)Source of chirality: AD-mix β

(2S,3S)-2,3-Dihydroxy-3-(5-phenyl-thiophen-2-yl)-propionic acid ethyl esterC15H16O4SEe = 98%[α]D20=+6.6 (c 0.5, CHCl3)Source of chirality: AD-mix β

(2S,3R)-2,3-Dihydroxy-4-thiophen-2-yl-butyric acid ethyl esterC10H14O4SEe = 94%[α]D20=+24.4 (c 1.5, CHCl3)Source of chirality: AD-mix β

(2S,3R)-2,3-Dihydroxy-4-(4-phenyl-thiophen-2-yl)-butyric acid ethyl esterC16H18O4SEe = 88%[α]D20=+26.6 (c 0.5, CHCl3)Source of chirality: AD-mix β

(2S,3R)-4-Benzo[b]thiophen-2-yl-2,3-dihydroxy-butyric acid ethyl esterC14H16O4SEe = 88%[α]D20=+36.7 (c 1.8, CHCl3)Source of chirality: AD-mix β

(2S,3R)-4-Benzo[b]thiophen-3-yl-2,3-dihydroxy-butyric acid ethyl esterC14H16O4SEe = 82%[α]D20=+18.8 (c 1.05, CHCl3)Source of chirality: AD-mix β