Tetrahydrofuran → HCID 57857034, compound

Participants

Reaction Steps

4-Carboxybutyltriphenylphosphonium bromide (3.5 molar equivalents) is suspended in anhydrous THF under a nitrogen atmosphere. Potassium tert-butoxide (1 M in THF, 7 molar equivalents) is added dropwise to the white suspension. The reaction mixture becomes bright red over the course of the addition and is subsequently stirred for 30 minutes at room temperature, then cooled to −15° C. in an ice/NaCl bath. The lactol (3aR,4R,5R,6aS)-4-((R,E)-3-(benzo[b]thiophen-2-yl)-3-(tert-butyldiphenylsilyloxy)prop-1-enyl)hexahydro-2H-cyclopenta[b]furan-2,5-diol (8a, limiting reagent) is dissolved in THF and added dropwise to the ylide. The reaction mixture becomes lighter orange in color and is additionally stirred for 2 hours at −15° C. and is then allowed to warm to room temperature and stir overnight. The reaction mixture becomes dark red. The reaction mixture is acidified with 5% aqueous KHSO4, diluted with brine (250 mL) and extracted with ethyl acetate (200 mL). The aqueous layer is extracted with another portion of ethyl acetate (50 mL) and the combined organic extracts are washed twice with brine (250 mL), dried over sodium sulfate, and evaporated to yield crude product. The crude product is purified by flash chromatography on regular silica gel using hexanes-ethyl acetate with 0.4% acetic acid as eluent to afford the title intermediate 9a.

Provenance & Evidence