Triethylammonium uridine 3 ,5 -cyclic

Triethylammonium uridine 3 5 -cyclic phosphate C-3 endo 0.64, 0.58 (two independent molecules3) 95... 

Triethylammonium uridine 3, 5 -cyclic phosphate153 5-Bromo-2 -deoxyuridine154 D-Arabinofuranosyl-5-bromouracil155 5-Bromouridine154 5-Bromouridine-methyl sulfoxide complex156... 

In this context, it is interesting to note that the first synthesis of 2, 3 -0,0-cyclic phosphorothioate 22a was reported by Eckstein in 1968 [25], He also isolated pure Rp diastereomer by fractional crystallization of the triethylammonium salts [26] and used it as reference to determine the absolute configurations of the other phosphorothioate analogues [27], 2, 3 -0,0-Cyclic H-phosphonate 20a was used as a key substrate for the synthesis of uridine 2, 3 -0,0-cyclic boranophosphate 27. Silylation of H-phosphate 20a gave the phosphite triester 25 (two diastereomers). Its boronation, with simultaneous removal of the trimethylsilyl group, was achieved by its reaction with borane-A.A-diisopropylethylamine complex (DIPEA-BH3). 

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