Triphenylphosphine → tert-butyl (3R,4R)-3-(4-tert-butoxy-benzoylamino)-4-(4-tert-butoxy-benzoyloxy)-azepan-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

262 mg of diethyl azadicarboxylate in 2 ml of tetrahydrofuran were added while stirring to 407 mg of the compound prepared in Example 16, 253 mg of 4-(tert-butoxy)-benzoic acid and 394 g of triphenylphosphine in 8 ml of tetrahydrofuran. After stirring at 50° C. for 4 hours, the solvent was removed under reduced pressure and the residue was taken up in 20 ml of cyclohexane and washed once with 20 ml of water and twice with 10 ml of 70% methanol/water each time. The aqueous-alcoholic phase was extracted twice with 10 ml of cyclohexane each time. The combined cyclohexane phases were dried over sodium sulphate and the solvent was removed under reduced pressure. The residual viscous oil was dissolved in 10 ml of hot heptane, seeded with pure end product and left to crystallize at room temperature for 18 hours and yielded 241 mg of tert-butyl (3R,4R)-3-(4-tert-butoxy-benzoylamino]-4-(4-tert-butoxy-benzoyloxy)-azepan-1-carboxylate of melting point 126-128° C. This compound can be reacted further as in Example 12b.

Provenance & Evidence