@article { ISI:000231782100007, title = {Unusual stereochemical outcome of radical cyclization: synthesis of (+)-biotin}, journal = {Tetrahedron}, volume = {61}, number = {39}, year = {2005}, month = {SEP}, pages = {9273-9280}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

An enantioselective synthesis of (+)-biotin 1 starting from naturally available cysteine is described. The key steps are the unusual stereochemical outcome of radical cyclization of compound 10 to prepare 5,5-fused system 11, and the introduction of C4-sidechain at C-6 in 13 via a Grignard reaction. (c) 2005 Elsevier Ltd. All rights reserved.

}, keywords = {biotin, exocyclization, radical cyclization}, issn = {0040-4020}, doi = {10.1016/j.tet.2005.07.070}, author = {Chavan, Subhash P. and Chittiboyina, A. G. and Ramakrishna, G. and Tejwani, R. B. and Ravindranathan, T. and Kamat, Subhash K. and Rai, B. and Sivadasan, L. and Balakrishnan, K. and Ramalingam, S. and Deshpande, V. H.} } @article { ISI:000259104700034, title = {Multi-component carbon-carbon bond forming Mannich reaction catalyzed by yttria-zirconia based Lewis acid}, journal = {Catalysis Communications}, volume = {9}, number = {14}, year = {2008}, month = {AUG}, pages = {2445-2448}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A direct three component Mannich-type reaction of aldehyde, amine, and ketone (without silyl enolates) were efficiently catalyzed by yttria-zirconia based strong Lewis acid in aqueous acetonitrile. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {beta-amino carbonyls, Mannich reaction, multi-component reaction, yttria-zirconia based Lewis acid}, issn = {1566-7367}, doi = {10.1016/j.catcom.2008.06.011}, author = {Ramalingam, S. and Kumar, Pradeep} } @article { ISI:000259412500023, title = {Synthesis of alpha-amino phosphonates by three component condensation of carbonyl compound, amine, and dialkyl phosphite using Yttria-zirconia based Lewis acid catalyst}, journal = {Catalysis Letters}, volume = {125}, number = {3-4}, year = {2008}, month = {OCT}, pages = {315-319}, publisher = {SPRINGER}, type = {Article}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

An efficient Yttria-zirconia Lewis acid catalyzed one-pot synthesis of alpha-amino phosphonates by three component coupling reaction of a carbonyl compound amine and dialkyl phosphates is described in good to high yield.

}, keywords = {alpha-amino phosphonates, three component coupling, Yttria-zirconia based Lewis acid catalyst}, issn = {1011-372X}, doi = {10.1007/s10562-008-9562-x}, author = {Ramalingam, S. and Kumar, Pradeep} } @article { ISI:000263875000017, title = {Yttria-zirconia-based lewis acid catalysis of the biginelli reaction: an efficient one-pot synthesis of 3,4-dihydropyrimidin-2-(1H)-ones}, journal = {Synthetic Communications}, volume = {39}, number = {7}, year = {2009}, month = {MAR}, pages = {PII 909239399}, publisher = {TAYLOR \& FRANCIS INC}, address = {325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA}, abstract = {

Yttria-zirconia-based Lewis acid efficiently catalyzes the three-component cyclocondensation reaction of aldehyde, -keto ester, and urea or thiourea in refluxing acetonitrile to produce the corresponding dihydropyrimidones in high yields.

}, keywords = {Biginelli reaction, dihydropyrimidone, yttria-zirconia-based Lewis acid}, issn = {0039-7911}, doi = {10.1080/00397910802519174}, author = {Ramalingam, S. and Kumar, Pradeep} } @article { ISI:000324460900018, title = {Concise synthesis of (5R,6S)-tert-butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine-1(2H)-carboxylate}, journal = {Arkivoc}, number = {2}, year = {2013}, month = {OCT}, pages = {220-227}, publisher = {ARKAT USA INC}, address = {C/O ALAN R KATRITZKY, UNIV FLORIDA, DEPT CHEMISTRY, PO BOX 117200, GAINESVILLE, FL 32611 USA}, abstract = {

An efficient synthesis of (5R,6S)-tert-butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine-1(2H)-carboxylate 1, a common intermediate for various polyhydroxylated piperidines is reported in six steps with 32\% overall yield starting from Garner{\textquoteright}s aldehyde. The key steps include the diastereoselective nucleophilic addition and intramolecular cyclization. (5R,6S)-tert-butyl 5-acetoxy-6-(hydroxymethyl)-5,6-dihydropyridine-1(2H)-carboxylate is a common precursor for the synthesis of 1-deoxy-L-mannojirimycin, 1-deoxy-L-idonojirimycin, L-fagomycin and related analogues.

}, keywords = {cyclization, Garner{\textquoteright}s aldehyde, nucleophilic addition, polyhydroxy piperidines}, issn = {1551-7004}, author = {Ramalingam, S. and Bhise, Ankushkumar D. and Show, Krishanu and Kumar, Pradeep} }