tert-Butyl (4R,6S)-6-(Bromomethyl)-2,2-dimethyl-1,3-dioxane-4-acetate → (4R-cis)-6-[(Acetyloxy)methyl]-2,2-dimethyl-1,3-dioxane-4-acetic acid, 1,1-dimethylethyl ester

Participants

Reaction Conditions

Reaction Steps

Solid tetrabutylammonium acetate (62.1 g, 0.207 mole, commercially available reagent was used) was added in one portion to a stirring solution of the bromoacetonide obtained in step (c) above (22.3 g, 0.068 mole) in 1-methyl-2-pyrrolidinone (276 ml, commercially available HPLC grade, used as purchased) under an argon atmosphere. The resulting solution was stirred at 90° C. (external temperature) for 1 hour (after a few minutes the reaction mixture became brown in color) to complete the reaction. (The progress of the reaction was followed by TLC, Rf =0.48 for the title product; Rf =0.63 for the bromoacetonide starting material (Silica gel, Ethyl acetate:Hexane, 1:1, visualization by Ce(SO4)2 spray).) The reaction mixture was cooled to room temperature and poured into water (1.5 L) and extracted with heptane (4×800 ml). The organic layers were combined and washed with water, brine, dried over MgSO4, filtered and concentrated under reduced pressure to furnish 18.45 grams of a brown solid. It was dissolved in heptane (250 ml) and treated with neutral NORIT® (25 grams).

Provenance & Evidence