The first total synthesis of rebaudioside R.

With easily available monosaccharides and steviol as starting materials, the first total synthesis of rebaudioside R with a xylosyl core in the C13-OH linked sugar chain was accomplished via two distinct approaches. The first approach features the stepwise installation of branch-sugar residues via an order of C2-OH first and then C3-OH of the xylosyl core, laying a firm foundation for the synthesis of analogues with different branch sugars, while the second route features the introduction of the C13 trisaccharide sugar chain via a convergent strategy, securing the overall synthetic efficiency. Through the synthetic study, the effect of protecting groups (PGs) at the vicinal hydroxy group on the reactivity of OH acceptors was illustrated.

The Structural Revision and Total Synthesis of Carambolaflavone A.

The synthesis of both enantiomers of carambolaflavone A, the antidiabetic and flavonoid C-glycoside, was achieved for the first time via a 12-longest-linear-step with 16% (l-fucose) and 11% (d-fucose) overall yields. Through the synthetic investigation, the adverse effect of 4A MS in Suzuki C-glycosylation was disclosed, the mechanism of hydrogen-bonded-phenol involved Suzuki C-glycosylation was clarified, and the authentic structure of carambolaflavone A was also determined.

1-(4-Chloro-phen-yl)-2-(1,3-diazepan-2-yl-idene)ethanone.

In the title compound, C13H15ClN2O, there are two crystallographically independent but conformationally similar (E)-mol-ecules in the asymmetric unit [dihedral angles between the phenyl ring and a common planar fragment of the 1,3-diazepane moiety = 47.34 (16) and 48.00 (16)°]. The seven-membered ring system adopts a chair conformation in both molecules. In the crystal, N-H⋯O hydrogen bonds lead to chains extending along the b-axis direction.

[6-(Furan-2-yl)-7-nitro-2,3,4,6,7,8-hexa-hydro-1H-pyrido[1,2-a]pyrimidin-9-yl](phen-yl)methanone.

The asymmetric unit of the title compound, C19H19N3O4, contains two mol-ecules with very few conformational differences; a C atom in the pyrimidine ring in one of the mol-ecules is disordered in a 0.688 (15):0.312 (15) ratio. In both mol-ecules, the fused pyridine and pyrimidine rings adopt half-chair conformations. The dihedral angles between the furan and benzene rings are 81.00 (13) and 84.99 (10)° in the two mol-ecules. The mol-ecular structure is consolidated by intra-molecular N-H⋯O hydrogen bonding. In the crystal, C-H⋯O hydrogen bonds connect the molecules into a three-dimensional network.

3,3-Bis(methyl-sulfan-yl)-1-(4-nitro-phen-yl)prop-2-en-1-one.

In the title compound, C11H11NO3S2, the S-Csp (2) bonds are shorter [1.746 (3) and 1.750 (2) Å] than the S-CH3 bonds [1.794 (3) and 1.806 (3) Å], which we attribute to d-π inter-actions between the S atoms and the C=C bond. The 1,1-bis-(methyl-sulfan-yl)-3-oxo-propyl-ene fragment and the 4-nitro-phenyl group are both almost planar, with the largest deviations from their mean planes being 0.053 (1) and 0.017 (2) Å, respectively. The dihedral angle between the two planes is 35.07 (7)°. Mol-ecules in the crystal are linked into a three-dimensional network by C-H⋯S and C-H⋯O hydrogen bonds.

[Survey on recent infection of human immunodeficiency virus among men who have sex with men in Tianjin during 2008 - 2009].

OBJECTIVE: To study the situation of HIV infections among men who have sex with men (MSM) in Tianjin during 2008 - 2009 and to provide reasonable evidence for intervention strategy. METHODS: Transect investigations in MSM were conducted three times during 2008 - 2009. Blood samples were collected and detected to identify the recent HIV infection with IgG-capture BED-enzyme immunoassay (BED-CEIA) before HIV incidence was estimated. RESULTS: 1799 specimens were tested and the HIV prevalence rates of each study were 6.7%, 8.6% and 6.2%, while the incidence rates were 2.7%, 2.5% and 2.8%, respectively. The estimated incidence rates among these testees were 5.36% and 5.52% per year in 2008 and 2009. RESULTS: of this study showed that the HIV incidence stabilized at high level among MSM in Tianjin, calling for the effective interventions be taken for HIV/AIDS control and prevention.