1.First total synthesis of antihypertensive natural products S-(+)-XJP and R-(-)-XJP.
Wang C1, Wei G, Yang X, Yao H, Jiang J, Liu J, Shen M, Wu X, Xu J. Org Biomol Chem. 2014 Oct 7;12(37):7338-44. doi: 10.1039/c4ob01470g.
The first asymmetric total synthesis of antihypertensive natural products S-(+)-XJP and R-(-)-XJP has been achieved in 8 steps starting from commercially available 6-bromo-2-hydroxy-3-methoxybenzaldehyde. Key steps included intramolecular Heck reaction and oxidative ozonolysis reaction with the retention of stereochemistry. A latent functionality strategy was implemented to circumvent the racemization in this endeavor. The protocol described here provided a fast and easily accessible synthetic method to obtain optically pure isochroman-4-one derivatives. Furthermore, the in vivo antihypertensive effects of (±)-XJP, S-(+)-XJP and R-(-)-XJP were investigated on spontaneously hypertensive rats. The obtained results could provide valuable information to identify a promising lead for further chemical modification research.
2.Mechanisms Responsible for High Energy Radiation Induced Damage to Single-Stranded DNA Modified by Radiosensitizing 5-Halogenated Deoxyuridines.
Wang S1, Zhao P1, Zhang C1, Bu Y1. J Phys Chem B. 2016 Mar 17;120(10):2649-57. doi: 10.1021/acs.jpcb.5b11432. Epub 2016 Mar 3.
Experimental studies showed that high energy radiation induced base release and DNA backbone breaks mainly occur at the neighboring 5' nucleotide when a single-stranded DNA is modified by radiosensitizing 5-halogenated deoxyuridines. However, no mechanism can be used to interpret these experimental observations. To better understand the radiosensitivity of 5-halogenated deoxyuridines, mechanisms involving hydrogen abstraction by the uracil-5-yl radical from the C2' and C3' positions of an adjacent nucleotide separately followed by the C3'-O3' or N-glycosidic bond rupture and the P-O3' bond breakage are investigated in the DNA sequence 5'-TU(•)-3' employing density functional theory calculations in the present study. It is found that hydrogen abstractions from both positions are comparable with the one from the C2' site slightly more favorable. The N-glycosidic bond cleavage in the neighboring 5' nucleotide following the internucleotide C2'-Ha abstraction is estimated to have the lowest activation free energies, indicating that the adjacent 5' base release dominates electron induced damage to single-stranded DNA incorporated by 5-halogenated deoxyuridines.
3.Crystal structure of ethyl 6-bromo-2-[(E)-2-phenyl-ethen-yl]quinoline-4-carboxyl-ate.
Shrungesh Kumar TO1, Naveen S2, Kumara MN3, Mahadevan KM4, Lokanath NK5. Acta Crystallogr E Crystallogr Commun. 2015 Jan 17;71(Pt 2):o121. doi: 10.1107/S2056989014028266. eCollection 2015.
In the title compound, C20H16BrNO2, the dihedral angle between the quinolone ring system mean plane (r.m.s. deviation = 0.018 Å) and the phenyl ring bridged by the ethynyl group, is 25.44 (14)°. There is an intra-molecular C-H⋯O hydrogen bond forming an S(6) ring motif. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds forming chains propagating along the b-axis direction.
4.Crystal structure of (6-bromo-2-oxo-2H-chromen-4-yl)methyl morpholine-4-carbodi-thio-ate.
Kumar KM1, Roopashree KR2, Vinduvahini M3, Kotresh O1, Devarajegowda HC2. Acta Crystallogr E Crystallogr Commun. 2015 Jun 13;71(Pt 7):o489-90. doi: 10.1107/S2056989015011007. eCollection 2015.
In the title compound, C15H14BrNO3S2, the 2H-chromene ring system is nearly planar, with a maximum deviation of 0.034 (2) Å, and the morpholine ring adopts a chair conformation. The dihedral angle between best plane through the 2H-chromene ring system and the morpholine ring is 86.32 (9)°. Intra-molecular C-H⋯S hydrogen bonds are observed. In the crystal, inversion-related C-H⋯S and C-H⋯O inter-actions generate R 2 (2)(10) and R 2 (2)(8) rings patterns, respectively. In addition, the crystal packing features π-π inter-actions between fused benzene rings [centroid-centroid distance = 3.7558 (12) Å].