@article { ISI:000260290900014, title = {Diastereoselective addition of planar N-heterocycles to vinyl sulfone-modified carbohydrates: a new route to isonucleosides}, journal = {Tetrahedron}, volume = {64}, number = {45}, year = {2008}, month = {NOV}, pages = {10406-10416}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Michael-type addition reactions of planar N-heterocycles at the C-2 positions of vinyl sulfone-modified carbohydrates provide an efficient and general route for the carbon-N-heterocycle bond formation. Therefore, the addition pattern of planar heterocycles, such as imidazole, triazole, thymine, and adenine to 3-C-phenyisulfonyl-hex-2-enopyranosides (1 alpha/1 beta) and 3-C-p-toluenesulfonyl-pent-2-enofuranosides (2 alpha/2 beta) was studied for developing a general methodology for the synthesis of new classes of isonucleosides possessing a carbon-N-heterocycle linkage at C-2 positions of furanosyl and pyranosyl sugars. To a great extent, the anomeric configurations of the starting vinyl sulfones play crucial roles in deciding the diastereoselectivity of addition of heterocycles. However, the trityl protected 3-C-p-toluenesulfonyl-hex-2-enopyranosides (33 alpha/33 beta) were judged to be More practical starting materials for desulfortylation and deprotection for the synthesis of a new class of thymine and adenine deoxyisonucleosides. (C) 2008 Elsevier Ltd. All rights reserved.

}, issn = {0040-4020}, doi = {10.1016/j.tet.2008.08.050}, author = {Sanki, Aditya K. and Bhattacharya, Rahul and Atta, Ananta Kumar and Suresh, Cheravakkattu G. and Pathak, Tanmaya} } @article { ISI:000256004800004, title = {Studies on the synthesis and unusual behavior of vinyl sulfone-modified hexenopyranosylthymines}, journal = {Carbohydrate Research}, volume = {343}, number = {7}, year = {2008}, month = {MAY}, pages = {1163-1170}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Although vinyl sulfone-modified- (VSM) pent-2-enofuranosyl nucleosides 2 and hex-2-enopyranosyl glycoside 4 are easily synthesized from the corresponding mesylated sulfones le and 3c, respectively, via an oxidation-mesylation-elimination route, the 3{\textquoteright}-C-sulfonyl-hex-2{\textquoteright}-enopyranosylthymine 11 is not obtained from 10 and a glycal derivative 12 is formed instead. On the other hand, 3-C-sulfonyl-hex-3{\textquoteright}-enopyranosylthymine 20 is easily synthesized from the mesylated sulfone 19. Again unlike the reaction patterns of VSM-pent-T-enofuranosyl nucleosides 2 and hex-2-enopyranosyl glycosides 4 as Michael acceptors, the reactions of nucleophiles with 3{\textquoteright}-C-sulfonyl-hex-3{\textquoteright}-enopyranosylthymine 20 yielded a rearranged product 21 instead of Michael adducts. (c) 2008 Published by Elsevier Ltd.

}, keywords = {glycal, hexopyranosyl nucleosides, Michael addition, unsaturated nucleosides, vinyl sulfone-modified nucleosides}, issn = {0008-6215}, doi = {10.1016/j.carres.2008.02.016}, author = {Deshpande, Sachin G. and Suresh, Cheravakkattu G. and Pathak, Tanmaya} } @article { ISI:000256613900001, title = {Unusual addition of amines to C-2 of vinyl sulfone-modified-beta-D-pent-2-enofuranosyl carbohydrates: synthesis of a new class of beta-anomeric 2-amino-2,3-dideoxy-D-threo-pentofuranosides}, journal = {Carbohydrate Research}, volume = {343}, number = {8}, year = {2008}, month = {JUN}, pages = {1287-1296}, publisher = {ELSEVIER SCI LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

When 3-C-sulfonyl-pent-2-enofuranosides and 3-C-sulfonyl-hex-2-enofuranosides were reacted with primary and secondary amines, only the beta-anomeric methoxy group of the pent-2-enofuranoside did not cause any hindrance to incoming nitrogen nucleophiles. This resulted in the {\textquoteleft}unusual{\textquoteright} addition of amines, in which the diastereoselectivity of the reaction was overwhelmingly in favor of amino sugars of the D-arabino configuration. Selected products were desulfonylated to obtain a new class of beta-anomeric 2-amino-2,3-dideoxy-D-threo-pentofuranosides. (C) 2008 Elsevier Ltd. All rights reserved.

}, keywords = {amino sugars, deoxyaminosugars, desulfonylation with Mg-MeOH-NiBr(2), diastereoselective Michael addition, vinyl sulfone-modified carbohydrates}, issn = {0008-6215}, doi = {10.1016/j.carres.2008.03.022}, author = {Das, Indrajit and Suresh, Cheravakkattu G. and Decout, Jean-Luc and Pathak, Tanmaya} }