38261-81-3Relevant articles and documents
Conformational effect on macroscopic chirality modification of cholesteric mesophases by photochromic azobenzene dopants
Ruslim, Christian,Ichimura, Kunihiro
, p. 6529 - 6535 (2000)
Azobenzenes having different positional substituents were dissolved in cholesteric liquid crystals to make cholesteric pitches tunable by photoisomerization. E-to-Z photoisomerization of 3,3′-disubstituted or 2,2′-dimethyl-3,3′-disubstituted azobenzenes resulted in a moderate change or even no change in the maximum wavelengths of reflectivity of the cholesteric phase, whereas azobenzene or 4,4′-disubstituted azobenzenes showed much bigger changes. The different in the conformations between the E- and Z-isomers of the azobenzenes is discussed to explain the observed characteristics. The photoinduced modification of helical pitches by photoisomerization of achiral azobenzenes was identical between a pair of enantiomeric cholesteric solvents, suggesting no preferred intrinsic handedness of the achiral azobenzenes. Experimental results with the corresponding chiral azobenzene suggested that the contribution of the conformation of the azobenzene to the effective helical twisting power is more pronounced than that of the molecular chirality arising from the asymmetric carbon at the terminal alkyl substituents. The photoinduced shortening or lengthening of the helical pitch seems to be determined crucially by the thermal characteristics of the cholesteric liquid crystals.
Absolute configuration at the tricarballylic acid moieties of fumonisin B2
Boyle, Craig D.,Kishi, Yoshito
, p. 4579 - 4582 (1995)
The configuration at the chiral centers of the two tricarallylic acid moieties of fumonisin B2 is shown to be R. This stereochemistry is opposite to that recently suggested by others for the tricarballylic acid portions of fumonisin B1 and AAL toxin T(A).
Structure-Elucidating Total Synthesis of the (Polyenoyl)tetramic Acid Militarinone C §
Brückner, Reinhard,Drescher, Christian,Hamburger, Matthias,Keller, Morris,Potterat, Olivier
supporting information, (2020/03/30)
The (polyenoyl)tetramic acid militarinone C (1) heads a family of seven members. Before our work, the configuration of C-5 was unknown whereas the configurations of C-8′ and C-10′ were either (R,R) or (S,S). We synthesized the four stereoisomers of constitution 1, which conform with these insights. This included cross-coupling both enantiomers of the western building block (8) with both enantiomers of the eastern building block (9). The specific rotations of the resulting 1 isomers suggested that natural 1 is configured like the coupling partners (S)-8 and (R,R)-9. This conclusion was corroborated by degrading natural 1 to alcohol 35 and by proving its configurational identity with synthetic (R,R)-35.
Studies on tridecaptin B1, a lipopeptide with activity against multidrug resistant Gram-negative bacteria
Cochrane, Stephen A.,Lohans, Christopher T.,Van Belkum, Marco J.,Bels, Manon A.,Vederas, John C.
, p. 6073 - 6081 (2015/06/08)
Previously other groups had reported that Paenibacillus polymyxa NRRL B-30507 produces SRCAM 37, a type IIA bacteriocin with antimicrobial activity against Campylobacter jejuni. Genome sequencing and isolation of antimicrobial compounds from this P. polymyxa strain show that the antimicrobial activity is due to polymyxins and tridecaptin B1. The complete structural assignment, synthesis, and antimicrobial profile of tridecaptin B1 is reported, as well as the putative gene cluster responsible for its biosynthesis. This peptide displays strong activity against multidrug resistant Gram-negative bacteria, a finding that is timely to the current problem of antibiotic resistance.