@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:000350763600017, title = {Total and semi-syntheses of antimicrobial thuggacin derivatives}, journal = {Chemistry-A European Journal}, volume = {21}, number = {11}, year = {2015}, month = {MAR}, pages = {4272-4284}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

The total and semi-synthesis of 13 new macrolactones derived from thuggacin, which is a secondary metabolite from the myxobacterium Sorangium cellulosum, are reported. The thuggacins have attracted much attention due to their strong antibacterial activity, particularly towards Mycobacterium tuberculosis. This study focuses on 1) thuggacin derivatives that cannot equilibrate by transacylation between the three natural thuggacins A-C, 2) the roles of the thiazole ring, and 3) the hexyl side chain at C2. Semi-synthetic O-methylation at C17 suppressed the transacylations without a substantial loss of antibacterial activity. Exchanging the C17-C25 side chain for simplified hydrophobic chains led to complete loss of antibacterial activity. Exchange of the thiazole by an oxazole ring or removal of the hexyl side chain at C2 had no substantial effect on the biological properties.

}, keywords = {antibiotics, lactones, Natural products, synthesis design, Total synthesis}, issn = {0947-6539}, doi = {10.1002/chem.201405874}, author = {Franke, Jana and Bock, Martin and Dehn, Richard and Fohrer, Joerg and Mhaske, Santosh B. and Migliorini, Antonella and Kanakis, Argyrios A. and Jansen, Rolf and Herrmann, Jennifer and Mueller, Rolf and Kirschning, Andreas} } @article {44654, title = {First total synthesis of the proposed structure of pandangolide 1}, journal = {European Journal of Organic Chemistry}, year = {2018}, month = {JUL}, pages = {3352-3364}, abstract = {

The first total synthesis of the proposed structure of pandangolide 1 is reported. The synthesis was carried out using both an organocatalytic approach and a chiral-pool approach. The required stereochemistry at C-3 and C-5 was installed by using an organocatalytic aldol reaction and a stereoselective ketone reduction. The construction of the 12-membered core was achieved by 2-methyl-6-nitrobenzoic anhydride-mediated Shiina lactonization. The structure of target molecule was confirmed unambiguously by single-crystal X-ray analysis, but the optical rotation and NMR spectroscopic data of the synthetic pandangolide 1 were found to be inconsistent with the natural product.

}, keywords = {lactones, Macrocycles, Natural products, structure elucidation, synthesis design, Total synthesis}, issn = {1434-193X}, doi = {10.1002/ejoc.201800675}, author = {Show, Krishanu and Gonnade, Rajesh G. and Kumar, Pradeep} } @article {47586, title = {Polyoxometalate clusters: inorganic ligands for functional materials}, journal = {Journal of Cluster Science}, volume = {33}, year = {2022}, month = {SEP}, type = {Review}, abstract = {

Research in polyoxometalates (POMs) is a diverse growing field with variations in application. POMs are consisting of metal ion and oxide. Peripheral oxides of POM can share spare electron pairs to behave as ligands. This property of POM was utilized for constructing coordination polymers (CPs), synthesizing transitional metal substituted POM for catalysis, synthesizing and stabilizing nano-particles, etc. POM connected structures have provided an opportunity of heterogenization of some homogeneous POM catalyst. Furthermore, diamagnetic POM ligands have been suitable for stabilizing and isolating magnetic ions inside clusters. The scope of this review is to summarize the role of POMs as ligands to prepare POM based CPs, synthesize and stabilize metal nano-particles and isolate magnetic ion or unit.

}, keywords = {Coordination polymer, Inorganic ligand, materials science, polyoxometalates, synthesis design}, issn = {1040-7278}, doi = {10.1007/s10876-021-02110-8}, author = {Dey, Chandan} }