@article { ISI:000294656400011, title = {One-step stereospecific strategy for the construction of the core structure of the 5,11-methanomorphanthridine alkaloids in racemic as well as in optically pure form: synthesis of (+/-)-pancracine and (+/-)-brunsvigine}, journal = {European Journal of Organic Chemistry}, number = {24}, year = {2011}, month = {AUG}, pages = {4571-4587}, publisher = {WILEY-V C H VERLAG GMBH}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

The unique core structure of the complex pentacyclic 5,11-methanomorphanthridine has been constructed stereospecifically in one step by an intramolecular [3+2] cycloaddition of a non-stabilized azomethine ylide (AMY), generated by the sequential double desilylation of 14 using (AgF)-F-I as a one-electron oxidant. The formation of the single diastereomer in the key step is explained by the preferred transition state produced by endo attack of the AMY on the {\textquoteleft}{\textquoteleft}Re{\textquoteright}{\textquoteright} face of the dipolarophile. An asymmetric version of the cycloaddition using a chiral dipolarophile was applied to construct the core structure 68 with 63 \% ee. This strategy was successfully applied to the formal synthesis of (+/-)-pancracine and the total synthesis of (+/-)-brunsvigine. An unprecedented and interesting skeletal rearrangement product 49 was observed during the attempted assembly of the E ring from 46 through Horner-Wadsworth-Emmons reactions. Mechanisms involving azetidinium salt formation or the Grob-type fragmentation are advanced to explain the observed rearrangement.

}, keywords = {alkaloids, Azomethine ylides, Cycloaddition, Ring-closing metathesis, synthesis design}, issn = {1434-193X}, doi = {10.1002/ejoc.201100601}, author = {Pandey, Ganesh and Kumar, Ravindra and Banerjee, Prabal and Puranik, Vedavati G.} } @article { ISI:000310215100010, title = {Organocatalytic dynamic kinetic resolution via conjugate addition: synthesis of chiral trans-2,5-dialkylcyclohexanones}, journal = {Organic \& Biomolecular Chemistry}, volume = {10}, number = {41}, year = {2012}, month = {AUG}, pages = {8260-8267}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A novel strategy of initiating an organocatalysed dynamic kinetic resolution (dr up to 99 : 1 and er up to 94 : 6) for the synthesis of chiral trans-2,5-dialkylcyclohexanones by an asymmetric conjugate addition of dimethyl malonate on to 6-substituted cyclohexenones is reported.

}, issn = {1477-0520}, doi = {10.1039/c2ob26597d}, author = {Pandey, Ganesh and Adate, Priyanka A. and Puranik, Vedavati G.} } @article { ISI:000315168800015, title = {Orthanilic acid-promoted reverse turn formation in peptides}, journal = {Chemical Communications}, volume = {49}, number = {22}, year = {2013}, month = {JAN}, pages = {2222-2224}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Orthanilic acid (2-aminobenzenesulfonic acid, (S)Ant), an aromatic beta-amino acid, has been shown to be highly useful in inducing a folded conformation in peptides. When incorporated into peptide sequences (Xaa-(S)Ant-Yaa), this rigid aromatic beta-amino acid strongly imparts a reverse-turn conformation to the peptide backbone, featuring robust 11-membered-ring hydrogen-bonding.

}, issn = {1359-7345}, doi = {10.1039/c3cc40522b}, author = {Kale, Sangram S. and Priya, Gowri and Kotmale, Amol S. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} }