Synthesis of 4‐ β ‐D‐arabinofuranosyl‐5,6‐dihydro‐2 H ‐1,2,4‐thiadiazin‐3‐one 1,1‐dioxide and x‐ray diffraction analysis of its 2′,3‐anhydro precursor

Reaction of 2‐amino‐3′,5′‐bis( O‐tert ‐butyldimethylsilyl)‐β‐ D ‐arabinofuran[1′,2′:4,5]‐2‐oxazoline with 2‐chloroethylsulfonyl chloride in the presence of sodium bicarbonate followed by removal of the protecting groups gave 2′,3‐anhydro‐4‐β‐ D ‐arabinofuranosyl‐5,6‐dihydro‐2 H ‐1,2,4‐thiadiazin‐3‐one 1,1‐dioxide ( 5 ), which by treatment with ammonia was converted to 4‐β‐ D ‐arabinofuranosyl‐5,6‐dihydro‐2 H ‐1,2,4‐thiadiazin‐3‐one 1,1‐dioxide ( 6 ). The structure of compound 5 was unequivocally established by means of an x‐ray diffraction analysis. The compound crystallized in the space group P2 1 2 1 2 1 with unit cell dimensions a = 5.883(3), b = 9.352(2), c = 18.769(7) Å, Z = 4. Its structure was established by direct multisolution techniques and refined by the full matrix least squares method to a final R value of 0.058 for the 1515 reflections observed.