128441-03-2Relevant articles and documents
Application of Trimethylgermanyl-Substituted Bisphosphine Ligands with Enhanced Dispersion Interactions to Copper-Catalyzed Hydroboration of Disubstituted Alkenes
Xi, Yumeng,Su, Bo,Qi, Xiaotian,Pedram, Shayun,Liu, Peng,Hartwig, John F.
supporting information, p. 18213 - 18222 (2020/12/04)
We report the incorporation of large substituents based on heavy main-group elements that are atypical in ligand architectures to enhance dispersion interactions and, thereby, enhance enantioselectivity. Specifically, we prepared the chiral biaryl bisphosphine ligand (TMG-SYNPHOS) containing 3,5-bis(trimethylgermanyl)phenyl groups on phosphorus and applied this ligand to the challenging problem of enantioselective hydrofunctionalization reactions of 1,1-disubtituted alkenes. Indeed, TMG-SYNPHOS forms a copper complex that catalyzes hydroboration of 1,1-disubtituted alkenes with high levels of enantioselectivity, even when the two substituents are both primary alkyl groups. In addition, copper catalysts bearing ligands possessing germanyl groups were much more active for hydroboration than one derived from DTBM-SEGPHOS, a ligand containing 3,5-di-tert-butyl groups and widely used for copper-catalyzed hydrofunctionalization. This observation led to the identification of DTMGM-SEGPHOS, a bisphosphine ligand bearing 3,5-bis(trimethylgermanyl)-4-methoxyphenyl groups as the substituents on the phosphorus, as a new ligand that forms a highly active catalyst for hydroboration of unactivated 1,2-disubstituted alkenes, a class of substrates that has not readily undergone copper-catalyzed hydroboration previously. Computational studies revealed that the enantioselectivity and catalytic efficiency of the germanyl-substituted ligands is higher than that of the silyl and tert-butyl-substituted analogues because of attractive dispersion interactions between the bulky trimethylgermanyl groups on the ancillary ligand and the alkene substrate and that Pauli repulsive interactions tended to decrease enantioselectivity.
Remote chiral communication in coadsorber-induced enantioselective 2D supramolecular assembly at a liquid/solid interface
Chen, Ting,Li, Shu-Ying,Wang, Dong,Yao, Man,Wan, Li-Jun
supporting information, p. 4309 - 4314 (2015/04/14)
Remote chiral communication in 2D supramolecular assembly at a liquid/solid interface was investigated at the molecular level. The stereochemical information in a chiral coadsorber was transmitted over a flexible spacer with a length of up to five methylene groups to a 2D supramolecular assembly of achiral building blocks with the cooperation of specific hydrogen bonding between the chiral coadsorber and achiral building blocks and the confinement effect during 2D crystallization. When the position of the stereogenic center was changed with respect to the stereocontrolling moiety, an odd-even effect was found. A stereogenic center closer to the stereocontrolling moiety transmitted the stereochemical information to the 2D supramolecular assembly more reliably. This result is beneficial not only for mechanistic understanding of chiral communication in 2D supramolecular assembly on surfaces but also for the rational design of homochiral supramolecular assemblies on surfaces.
Synthesis, absolute stereochemistry and molecular design of the new antifungal and antibacterial antibiotic produced by Streptomyces sp.201
Boruwa,Kalita,Barua,Borah,Mazumder,Thakur,Gogoi,Bora
, p. 3571 - 3574 (2007/10/03)
The absolute stereochemistry of the new antifungal and antibacterial antibiotic produced by Streptomyces sp.201 has been established by achieving the total synthesis of the product. A series of analogues have also been synthesized by changing the side chain and their bioactivity assessed against different microbial strains. Among them, 1e (R=C8H17) was found to be the most potent with MIC of 8μg/mL against Mycobacterium tuberculosis, 12μg/mL against Escherichia coli and 16μg/mL against Bacillus subtilis 6μg/mL against Proteus vulgaris. This was followed by 1b (R=C5H11) with MIC of 10-20μg/mL range and 1d (R=C 7H15) with MIC of 14-24g/mL, whereas 1a (R=C 4H9) and 1f (R=C18H35) were found to be completely inactive. Besides, 1c (R=C6H13) showed certain extent of antibacterial activity in the range of 24-50μg/mL. Mycobacterium tuberculosis was very sensitive to 1e (R=C8H 17) with MIC of 8μg/mL. Antifungal activity of analogues 1d (R=C7H15) and 1e, (R=C8H17) against Fusarium oxysporum and Rhizoctonia solani were found promising with MFCs in the 15-18μg/mL range.
