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Nucleosides selective esterification

Product distributions obtained on esterification of nucleosides and nucleotides under basic conditions throw further light on factors affecting selective reactivity. p-Toluenesulfonylation of adenosine 5 -monophosphate in aqueous alkali yielded exclusively (in 54-61% yield) the 2 -p-toluenesulfonate.107 Lack of reaction at HO-3 was attributed either to formation of a phosphoric p-toluenesulfonic anhydride, which sterically protected this hydroxyl group, or to the higher acidity of HO-2. It has been shown that the acidic site (with pKa 12.5) in adenosine is associated with the presence of both HO-2 and HO-3, as replacement of either of these by hydrogen, or of HO-2 by methoxyl, results in loss of this acidity.108 Inductive effects, or the sta-... [Pg.33]

The above-described acylation of the sugar moiety of the nucleotide adenosine (3) [2] has been followed by a series of papers reporting on the chemoselec-tive enzymatic modification of natural compounds carrying both hydroxyl and amino groups. In addition to the extensive work on nucleosides developed by Gotor and coworkers [8], the biocatalyzed esterification of the hydroxylated alkaloids castanospermine (4) and 1-deoxynojirimidn (5) should be mentioned. Both compounds were selectively acylated at their C-6 and/or C-2 OH by the protease subtilisin, despite the presence of a potentially more reactive amino functions [9]. [Pg.146]


See other pages where Nucleosides selective esterification is mentioned: [Pg.13]    [Pg.48]    [Pg.31]    [Pg.554]    [Pg.48]    [Pg.688]    [Pg.676]    [Pg.303]    [Pg.303]    [Pg.20]   
See also in sourсe #XX -- [ Pg.33 , Pg.53 , Pg.59 ]




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