- DDQ mediated regiospecific protection of primary alcohol and deprotection under neutral conditions: Application of new p-methoxy benzyl-pixyl ether as reagent of choice for nucleoside protection
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A simple and efficient protocol is described for regiosepecific protection of primary hydroxyl group both in nucleosides and other molecules with p-methoxy-benzyl 2,7-dimethyl pixylether (MBDPE) in presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Furthermore, swift deprotection of 2, 7-dimethylpixyl (DMPx) is accomplished with DDQ in MeOH. Both procedures are successfully implemented on gram-scale synthesis of modified nucleosides. This protocol offers mild and neutral conditions for selective protection and deprotection of DMPx group while compatible in presence of other conventional protecting groups such as benzoyl, benzyl, THP, TBDPS and acetonide.
- Srishylam, Penjarla,Raji Reddy,Banerjee, Shyamapada,Penta, Santhosh,Sanghvi, Yogesh S.
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- Copper(II)nitrate catalyzed regioselective protection of primary alcohols with 4,4′-dimethoxytrityl and 2,7-dimethyl-9-phenyl xanthen-9-yl groups in nucleosides and carbohydrates
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Regioselective protection of primary hydroxyl group in nucleoside and carbohydrate analogs was accomplished using dimethoxytrityl alcohol (DMTr-OH) or dimethylpixyl alcohol (DMPx-OH) in presence of copper(II)nitrate as a Lewis acid catalyst. Excellent selectivity was observed for the protection of primary hydroxyl group over secondary while glycosidic bond remain unaffected. Utility of this methodology was further exemplified via DMTr- and DMPx-protection of alipahtic acyclic and cyclic diols.
- Penjarla, Srishylam,Prasad, S. Rajendra,Reddy, Dhande Sudhakar,Banerjee, Shyamapada,Penta, Santhosh,Sanghvi, Yogesh S.
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p. 232 - 247
(2018/05/14)
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- Renewable amberlyst-15 catalyzed highly regioselective tritylation and deprotection of sugar-based diols
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Amberlyst-15 catalyzed highly regioselective tritylation of sugar-based diols was achieved under mild condition using 4,4′-dimethoxytrityl alcohol (DMTrOH). Deprotection of the corresponding DMTr group was also established by the variation to protic solvent. Meanwhile, the heterogeneous catalyst Amberlyst-15 was recycled 3 times with satisfactory retention of catalytic activity and proved its potential application in industry.
- Valeru, Anil,Luo, Zhibin,Penjarla, Srishylum,Khan, Imran,Liu, Bin,Sngepu, Bhavanarushi,Xu, Yin,Xie, Jimin
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p. 318 - 326
(2018/10/15)
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- Building blocks for the solution phase synthesis of oligonucleotides: Regioselective hydrolysis of 3′,5′-di-O-levulinylnucleosides using an enzymatic approach
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A short and convenient synthesis of 3′- and 5′-O-levulinyl-2′-deoxynucleosides has been developed from the corresponding 3′,5′-di-O-levulinyl derivatives by regioselective enzymatic hydrolysis, avoiding several tedious chemical protection/deprotection steps. Thus, Candida antartica lipase B (CAL-B) was found to selectively hydrolyze the 5′-levulinate esters, furnishing 3′-O-levulinyl-2′-deoxynucleosides 3 in >80% isolated yields. On the other hand, immobilized Pseudomonas cepacia lipase (PSL-C) and Candida antarctica lipase A (CAL-A) exhibit the opposite selectivity toward the hydrolysis at the 3′-position, affording 5′-O-levulinyl derivatives 4 in >70% yields. A similar hydrolysis procedure was successfully extended to the synthesis of 3′- and 5′-O-levulinyl-protected 2′-O-alkylribonucleosides 7 and 8. This work demonstrates for the first time application of commercial CAL-B and PSL-C toward regioselective hydrolysis of levulinyl esters with excellent selectivity and yields. It is noteworthy that protected cytidine and adenosine base derivatives were not adequate substrates for the enzymatic hydrolysis with CAL-B, whereas PSL-C was able to accommodate protected bases during selective hydrolysis. In addition, we report an improved synthesis of dilevulinyl esters using a polymer-bound carbodiimide as a replacement for dicyclohexylcarbodiimide (DCC), thus considerably simplifying the workup for esterification reactions.
- Garcia, Javier,Fernandez, Susana,Ferrero, Miguel,Sanghvi, Yogesh S.,Gotor, Vicente
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p. 4513 - 4519
(2007/10/03)
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