@article {47402, title = {Total synthesis of twelve membered resorcyclic acid lactones, (R)-penicimenolide A, (R)-resorcyclide and (R)-dihydroresorcyclide}, journal = {Tetrahedron}, volume = {85}, year = {2021}, month = {APR}, pages = {132059}, type = {Article}, abstract = {

Resorcyclic Acid Lactones or RALs are a class of fungal secondary polyketides isolated from a variety of fungal strains like Lasiodiplodia theobromae, Penicillium sp., Syncephalastrum racemosum etc. This class of macrocyclic lactones are found to exhibit a broad spectrum of biological activities and are of significant synthetic importance. Herein, we report the first total synthesis of (R)-penicimenolide A, twelve membered RAL (RAL12) isolated from Penicillium sp. (NO. SYP-F-7919). Besides, we also report the total synthesis of two other members, namely, (R)-trans-resorcyclide and (R)-dihydroresorcyclide. In the course of synthesis, we have utilized ring closing metathesis (RCM) as the key step in constructing the core macrolactone scaffold. (C) 2021 Elsevier Ltd. All rights reserved.

}, keywords = {Macrocycle, Natural product, organic synthesis, Total synthesis}, issn = {0040-4020}, doi = {10.1016/j.tet.2021.132059}, author = {Das, Pronay and Reddy, D. Srinivasa} } @article {48045, title = {Studies directed toward the total synthesis of nannocystin A}, journal = {ChemistrySelect}, volume = {7}, year = {2022}, month = {NOV}, pages = {e202203893}, type = {Article}, abstract = {

A full account of our efforts directed toward the stereoselective total synthesis of nannocystin A, a macrocyclic myxobacterial metabolite, is presented. In this endeavor, we have attempted two distinct synthetic routes to access polyketide fragment (C1-C11) of macrocyclic depsipeptide (21-membered) natural product from readily accessible building blocks 1,3-propanediol and benzaldehyde employing Evans aldol, CBS reduction, Heck cross-coupling, and Sharpless asymmetric epoxidation as key transformations. Ultimately, accomplished the synthesis of the complete skeleton (21-membered precursor for macrocyclic depsipeptide) of the nannocystin A possessing desired stereochemistry and functional groups.

}, keywords = {amidation, Depsipeptide, Evans aldol reaction, Macrocycle, Nannocystins}, issn = {2365-6549}, doi = {10.1002/slct.202203893}, author = {Nomula, Rajesh and Pratapure, Madhukar S. and Kontham, Ravindar} } @article {49139, title = {Zwitterionic tetrastanna(II) cyclic crown}, journal = {European Journal of Inorganic Chemistry}, volume = {26}, year = {2023}, month = {OCT }, type = {Article}, abstract = {

A 12-membered zwitterionic tetrastanna(II) cycle 1 having a crown ether-like topology has been isolated from the deprotonation of 1,1 \& PRIME;-methylenediimidazole (B) with two equivalents of Sn[N(SiMe3)(2)](2) (A). The solid-state structure and NMR analysis confirms the tetrastanna(II) cycle 1 to be comprised of two stannate(II) and two stannyliumylidene ion pairs in alternating positions of the heterocycle. Computational analysis shows greater nucleophilicity at the proximally located stannate(II) centers. Nonetheless, the tetrastanna(II) cycle 1 remains poorly reactive due to engagement of Sn-II lone pair electrons in intramolecular donor-acceptor interactions. Simple deprotonation reaction between Sn[N(SiMe3)(2)](2) (A) and N-(diisopropylphenyl)imidazole (C) in equimolar ratio has led to a stannylene 2, involving the formation of a Sn-C covalent bond with the anionic imidazol-2-yl carbon center along with the release of NH(SiMe3)(2). Compound 2 exists as a dimer, where the unsubstituted ring nitrogen atom coordinated intermolecularly to the other stannylene center.

}, keywords = {Deprotonation, Imidazole, Macrocycle, Sn-II cation, stannylene}, issn = {1434-1948}, doi = {10.1002/ejic.202300249}, author = {Sahoo, Padmini and Chibde, Purva and Das, Satyabrata and Banerjee, Subhrashis and Mali, Bhupendra P. and Vanka, Kumar and Gonnade, Rajesh G. and Yildiz, Cem. B. and Majumdar, Moumita} }