1: ethyl 2-deoxy-2,2-difluoro-D-erythro,D-threo-pentonate With toluene-4-sulfonic acid in water T=75 - 80°C; 3 h; 2: benzoyl chloride With pyridine; 4-(N,N-dimethlyamino)pyridine in ethyl acetate T=60 - 65°C; 3 h; Dean and Stark apparatus; Product distribution / selectivity;