@article { ISI:000345902500007, title = {Facile and convenient synthesis of (+/-)-Biotin via MgCl2/Et3N-mediated C-C coupling and mitsunobu reaction}, journal = {Synlett}, volume = {25}, number = {20}, year = {2014}, month = {DEC}, pages = {2879-2882}, publisher = {GEORG THIEME VERLAG KG}, type = {Article}, address = {RUDIGERSTR 14, D-70469 STUTTGART, GERMANY}, abstract = {

A synthesis of (+/-)-biotin is described starting from simple starting materials viz. cyclohexanone and amino malonic acid ester. The key steps involved are MgCl2/Et3N coupling of amino malonic acid ester derivative and acid chloride, Mitsunobu reaction, ozonolysis, Staudinger reduction, novel urea formation, and subsequent dibenzylation. This approach is economical and involves high-yielding steps and simple reaction conditions.

}, keywords = {Appel reaction, biotin, Mitsunobu reaction, Ozonolysis, Staudinger reduction}, issn = {0936-5214}, doi = {10.1055/s-0034-1379365}, author = {Chavan, Subhash P. and Chavan, Prakash N. and Lasonkar, Pradeep B. and Khairnar, Lalit B. and Kadam, Appasaheb L.} } @article {45487, title = {Synthesis of 3-azidopiperidine skeleton employing ceric ammonium nitrate (CAN)-mediated regioselective azidoalkoxylation of enol ether: total synthesis of d-2 receptor agonist (+/-)-quinagolide}, journal = {Organic letters }, volume = {20}, year = {2018}, month = {NOV }, pages = {7011-7014}, type = {Article }, abstract = {The total synthesis of (+/-)-quinagolide, which is a D-2 receptor agonist, was accomplished via a ceric ammonium nitrate (CAN)-mediated regioselective azidoalkoxylation of enol ether route. Key features of the synthesis include Claisen rearrangement, PPTS (pyridinium p-toluene-sulfonate)-catalyzed one-pot acetal deprotection, followed by a diastereoselective Henry reaction, which enables construction of the required trans ring junction and CAN-mediated regioselective azidoalkoxylation of enol ether. The PPTS-catalyzed intramolecular diastereoselective Henry reaction to fix three contiguous stereocenters on tetrahydronaphthalene and the first-of-its-kind synthesis of the 3-azidopiperidine skeleton, using a CAN -mediated regioselective azidoalkoxylation of enol ether, are important findings of the present work.}, issn = {1523-7060}, doi = { 10.1021/acs.orglett.8b02900}, author = {Chavan, Subhash P. and Kadam, Appasaheb L. and Lasonkar, Pradeep B. and Gonnade, Rajesh G.} } @article {46435, title = {Enantioselective formal total synthesis of (-)-quinagolide}, journal = {Organic Letters}, volume = {21}, year = {2019}, month = {NOV}, pages = {9089-9093}, type = {Article}, abstract = {

The enantioselective formal total synthesis of (-)-quinagolide has been accomplished in a linear sequence of 8 purification steps from pyridine. The key steps are (a) organocatalyzed Diets-Alder reaction for fixing all three stereocenters on piperidine ring; (b) protecting group enabled deoxygenation of isoquinuclidine skeleton under Birch reduction condition; (c) Lewis acid (TiCl4) catalyzed intramolecular Friedel-Crafts cyclization of dicarboxylic acid; and (d) one-pot diastereoselective ketone reduction-intramolecular cyclization to form oxazolidinone which enables trans-geometry installation. During the course of the synthesis, an interesting reductive cleavage of the C-N bond in the electron-deficient isoquinuclidine skeleton under the Birch reduction conditions has been observed. This is the first synthetic effort to access the core skeleton of (-)-quinagolide.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.9b03477}, author = {Chavan, Subhash P. and Kadam, Appasaheb L. and Gonnade, Rajesh G.} } @article {46115, title = {Total synthesis of (+/-)-quinagolide: a potent D-2 receptor agonist for the treatment of hyperprolactinemia}, journal = {ACS Omega}, volume = {4}, year = {2019}, month = {MAY}, pages = {8231-8238}, type = {Article}, abstract = {

A potent dopamine (D-2) receptor agonist (+/-)-quinagolide, which is used for the treatment of hyperprolactinemia, was synthesized using the ring closing metathesis (RCM) approach from meta-hydroxybenzaldehyde as the starting material. The key features of this synthesis are pyrolytic elimination, late-stage expedient synthesis of functionalized trans-fused tetrahydropyridine-3-carboxylates from olefin 6, via conjugate addition-elimination upon acetate 11, followed by RCM and phenyliodine bis(trifluoroacetate) (PIFA)-mediated Hofmann rearrangement of piperidine-3-carboxamide, which enables the synthesis of 3-aminopiperidine skeleton of quinagolide. For the total synthesis of natural products such as ergot alkaloids, late-stage synthesis of functionalized trans-fused tetrahydropyridine-3-carboxylates using RCM and PIFA-mediated Hofmann rearrangement of piperidine-3-carboxamide, which allows quick access to the synthetically challenging 3-aminopiperidine skeleton, are the main achievements of the present work.

}, issn = {2470-1343}, doi = {10.1021/acsomega.9b00903}, author = {Chavan, Subhash P. and Kadam, Appasaheb L. and Kawale, Sanket A.} } @article {46992, title = {Furan-derived chiral bicycloaziridino lactone synthon: collective syntheses of oseltamivir phosphate (Tamiflu), (S)-pipecolic acid and its 3-hydroxy derivatives}, journal = {Chemistry-An Asian Journal}, volume = {15}, year = {2020}, month = {FEB }, pages = {415-424}, type = {Article}, abstract = {

A unified synthetic strategy for oseltamivir phosphate (tamiflu), (S)-pipecolic acid, and its 3-hydroxy derivatives from furan derived common chiral bicycloaziridino lactone synthon is described here. Key features are the short (4-steps), enantiopure, and decagram-scale synthesis of common chiral synthon from furan and its first-ever application in the total synthesis of biologically active compounds by taking the advantages of high functionalization ability of chiral synthon.

}, keywords = {Aziridine synthon, Chiral auxiliary, collective synthesis, Pipecolic acid, Tamiflu}, issn = {1861-4728}, doi = {10.1002/asia.201901523, Early Access Date = JAN 2020}, author = {Chavan, Subhash P. and Kadam, Appasaheb L. and Shinde, Shrikrishna S. and Gonnade, Rajesh G.} } @article {46634, title = {Scalable synthesis of 3-Ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one: an important building block of the antidiabetic drug glimepiride}, journal = {Synthesis-Stuttgart}, volume = {52}, year = {2020}, month = {NOV}, pages = {3480-3484}, type = {Article}, abstract = {

A four-step, practical, and easily scalable synthesis of 3-ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one, an important building block of the antidiabetic drug glimepiride, has been accomplished. Key features are the synthesis of 3-methyl-4-hydroxy-2-butenolide in water and triflic acid mediated N-benzyl lactam N-deprotection. The main advantages of this process are the scalable synthetic route and decreased number of reaction steps, which paves the way for the industrial-scale synthesis of 3-ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one.

}, keywords = {antidiabetic drug, Butenolide, glimepiride, lactams, scalable synthesis}, issn = {0039-7881}, doi = {10.1055/s-0040-1707344}, author = {Chavan, Subhash P. and Pawar, Ambaji A. and Patil, Niteen B. and Kadam, Appasaheb L. and Shinde, Shrikrishna S.} } @article {47664, title = {Formal synthesis of (-)-quinagolide: diastereoselective ring expansion via a bicyclic aziridinium ion strategy to access the octahydrobenzo[g]quinoline architecture}, journal = {Journal of Organic Chemistry}, volume = {86}, year = {2021}, month = {JUL }, pages = {9344-9352}, type = {Article}, abstract = {The diastereoselective formal synthesis of (-)-quinagolide, a D-2 receptor agonist, has been achieved. The synthesis started from L-pyroglutamic acid and relied on utilization of (a) a stereospecific catalytic hydrogenation and diastereoselective Horner-Emmons-Michael cascade to obtain functionalized prolinate, (b) a Lewis acid mediated Pummerer cyclization to construct a tricyclic fused ring system, and (c) a diastereoselective ring expansion via a bicyclic aziridinium intermediate to access the required 3-substituted piperidine scaffold.}, issn = {0022-3263}, doi = {10.1021/acs.joc.1c00603}, author = {Chavan, Subhash P. and Kawale, Sanket A. and Pisal, Mahesh M. and Kadam, Appasaheb L. and Gonnade, Rajesh G.} } @article {48075, title = {Revisiting classical pummerer cyclization reaction: a key strategy for the synthesis of (+/-)-quinagolide}, journal = {ChemistrySelect}, volume = {7}, year = {2022}, month = {JUL}, pages = {e202201600}, type = {Article}, abstract = {

A formal synthesis of (+/-)-quinagolide using beta-alanine as a starting material has been achieved. Late stage intramolecular classical Pummerer reaction has been used as a key synthetic tool to construct octahydrobenzo[g]quinoline skeleton of quinagolide. Conjugative reduction of olefin, regioselective C-alkylation over O-alkylation of beta-ketoester followed by retro-Dieckmann/ Dieckmann reaction sequence has been used as a key reaction sequence to achieve prerequisite sulfoxide for the Pummerer reaction. While revisiting the classical Pummerer reaction, the one-pot sequential thionium ion induced cyclocarbamation followed by N-carbamate deprotection and Friedel-Crafts type Pummerer cyclization was observed as an important finding of the present work.

}, keywords = {Alkylation, Cyclocarbamation, Hyperprolactinemia, rearrangement, Thionium ion}, issn = {2365-6549}, doi = {10.1002/slct.202201600}, author = {Chavan, Subhash P. and Kawale, Sanket A. and Tripathi, Anupam and Kadam, Appasaheb L. and Gonnade, Rajesh G.} }