Synthesis of 2‘,3‘-Didehydro-2‘,3‘-dideoxynucleosides by Reaction of 5‘-O-Protected Nucleoside 2‘,3‘-Dimesylates with Lithium Areneselenolates

Synthesis of 2,3-Didehydro-2,3-dideoxynucleosides via Nucleoside Route.

“…Application of this methodology permitted the conversion of 5'-O-protected ribonucleosides into the corresponding 2',3'-di-O-mesylates which upon treatment with a variety of metallic dianions afforded the 2',3'-didehydro-2',3'-dideoxynucleosides (see Scheme 34) [111][112][113].…”

Estratégias para a síntese de desoxinucluosídeos

“…A mesma metodologia foi utilizada para a síntese de outros desidronucleosíde-os, como o d4T (42), cuja etapa de eliminação ocorreu com um rendimento de 57% [140][141][142] . 152 . Cerca de 50% do telúrio elementar usado na preparação dos sais pode ser recuperado da mistura reacional ao término da reação (Esquema 29).…”

Efficient Conversion of Vicinal Diols to Alkenes by Treatment of the Corresponding Dimesylates with a Catalytic, Minimally Fluorous, Recoverable Diaryl Diselenide and Sodium Borohydride

“…Like Clive, , we propose that these reactions proceed by S N 2 displacement of a first mesylate by the areneselenide anion, followed by closure to give a cyclic episelenenium ion, and final selenophilic attack by the second equivalent of selenide anion to liberate the product and regenerate the catalyst (Scheme ). Also like Clive, we find similar constraints imposed by steric hindrance; thus 2- exo -3- exo -camphanediol dimesylate was not a substrate for the present nor the original reaction, being recovered unchanged.…”

“…Clive and his group have described a protocol for the elimination of vicinal dimesylates to alkenes by treatment with areneselenide anions or with telluride dianion. , The nucleophiles were generated in situ by reduction of the diselenide or of tellurium, respectively, with lithium triethylborohydride or with sodium in liquid ammonia. Although, in view of the reasonable mechanisms proposed, the diselenide and tellurium metal, respectively, are necessarily regenerated in the course of the reaction, only one example, using bis(2,4-dimethoxyphenyl) ditelluride with ethanolic sodium borohydride as stoichiometirc reductant, was reported as being successful under catalytic conditions .…”

“…Here we describe a catalytic variant on Clive's protocol, employing a minimally fluorous diselenide, recoverable by continuous fluorous extraction. We also make use of sodium borohydride in ethanol as the reducing system and solvent, which eliminates the need for highly anhydrous media and for the addition of HMPA, which are characteristic of Clive's superhydride/THF/HMPA system. , …”