To a solution of (R)-2,2-Difluoro-9-hydroxy-6,7,8,9-tetrahydro-1,3-dioxa-5-aza-cyclohepta[f]indene-5-carboxylic acid tert-butyl ester (1.9 mmol) in Toluene, add DPPA (2.5 mmol) and DBU (2.5 mmol). After heating the mixture at 65° C. for 14 h, remove solvent under vacuum and chromatograph the intermediate using ethyl acetate/hexane (5-20%) to elute. This provides (S)-9-Azido-2,2-difluoro-6,7,8,9-tetrahydro-1,3-dioxa-5-aza-cyclohepta[f]indene-5-carboxylic acid tert-butyl ester as a colorless oil. To a solution of (S)-9-Azido-2,2-difluoro-6,7,8,9-tetrahydro-1,3-dioxa-5-aza-cyclohepta[f]indene-5-carboxylic acid tert-butyl ester (1.8 mmol) in methanol (20 mL) add a catalytic amount of Pd/C after purging the solution with nitrogen. Place a balloon of hydrogen on the reaction and purge the solution several times. After stirring for 1 h, purge the solution with nitrogen then filter through celite. Collect the filtrate and remove solvent under vacuum to provide the title compound as a colorless oil.
