Isobutyl chloroformate → meso-DAP (D)GlyOH

Participants

Reaction Steps

To a suspension of D-alanine (2.89 g) in a mixture of methylene chloride (30 ml) and dimethylformamide (12 ml) was added bis(trimethylsilyl)acetamide (30 ml) and the mixture was stirred for 15 hours at room temperature to give a clear solution. To a solution of the mixed anhydride of Z-(L)-Boc-(D)-mesoDAP-(D)-NHNHBoc (1) (13.45 g) in methylene chloride (140 ml), prepared by adding N-methylmorphorine (3.03 g) and isobutyl chloroformate (4.10 g) at -15° and stirring the mixture for 40 minutes at the same temperature, was added in one portion the above solution of D-alanine trimethylsilyl ester at -40° C. Then the reaction mixture was allowed to warm up to 0° C. and stirred for 2 hours. The reaction mixture was evaporated and the residue was dissolved in water, acidified with diluted hydrochloric acid and extracted with ethyl acetate. The extract was washed with water, dried over magnesium sulfate and concentrated to give a white powder (12.25 g) of Z-(L)-Boc-(D)-mesoDAP-(D)-NHNHBoc-(L)-D-AlaOH (2).

Provenance & Evidence