The syntheses of asunaprevir and declatasvir were described
in an earlier review article.Condensation of
indole-6-carboxylic acid (1) with cyclohexanone under basic
conditions gave acid 2 in quantitative yield. Hydrogenation of
the double bond in 2 using Pearlman?ˉs catalyst was followed by
esterification to give ester 3 in high yield. Bromination of the
indole at the 2-position was accomplished with pyridinium
tribromide, and this was followed by saponification to provide
acid 4. Treatment of 4 with carbonyldiimidazole (CDI)
followed by N,N- dimethylsulfamide and 1, 8 -
diazabicyclo[5.4.0]undec-7-ene (DBU) gave compound 5 in
74% yield. Suzuki coupling of 5 with commercial boronic acid 6
provided intermediate 7, which converted to hemiaminal 8
upon continued heating in 61% yield. Compound 8 was then
treated with methyl 2-(dimethoxyphosphoryl)acrylate (9) to
affect a tandem conjugate addition and Horner?Wadsworth?
Emmons (HWE) olefination to give ester 10. Alternatively, the
Suzuki coupling reaction of 5 with 6 could be stopped at
intermediate 7, which could be treated with 9 to promote the tandem conjugate addition/HWE to give 10. Corey?-Chaykovsky cyclopropanation of 10 using sodium hydride
and trimethylsulfoxonium iodide followed by chiral separation
provided cyclopropane 11 in good yield and >99% enantiomeric
excess (ee). Saponification of the methyl ester of 11
followed by coupling with 3-methyl-3,8-diazabicyclo[3.2.1]-
octane dihydrochloride (12) gave beclabuvir (I) in high yield.
