Four new polyhydroxylated steroids from the South Sea sponge Plakortis sp.

Four new polyhydroxylated steroids plaksterols A–D(1–4), together with two known related steroids ergost-7,9(11),22-trien-3β,5α,6α-triol(5) and ergosta-6β-methoxy-7,22-diene-3β,5α-diol(6), were isolated from methanol extract of the South China Sea marine sponge Plakortis sp. Their structures were identified by spectroscopic analysis, including NMR, MS, and IR. The cytotoxicity of the polyhydroxylated steroids were evaluated, and compound 6 showed moderate inhibitory activities against K562, HL-60 and BEL-7402 cells.

Synthesis of a novel C-branched polyhydroxylated cyclic nitrone

A novel C-branched polyhydroxylated cyclic nitrone 25.which could be a valuable intermediate for the synthesis of C-branched pyrrolidine iminosugars,was synthesized starting from the commercially available i.-arabinose in 29.0%total yield.

CO_(2) Adducts of the Amino and Imino Groups Studied by ~1HNMR and ^(13)CNMR

CO2 adducts of L-(+)-asparaginic acid and some polyhydroxylated alkaloids was studied by 1HNMR and 13CNMR in this paper.

Recent advances on the synthesis of natural pyrrolizidine alkaloids: alexine, and its stereoisomers

Natural products have attracted the interest of the scientific community due to their importance and application.Alexine is a naturally polyhydroxylated pyrrolizidine alkaloid that is broadly found in plant sources and isolated from Alexa leiopetala.The biological properties such as glycosidase inhibitors,anti-virus,and anti-HIV activities,makes it interesting target for synthetical studies.This review reports different approaches and methodologies to the synthesis of alexine,and its stereoisomers as the target compounds in numerous studies.

Synthesis of 6,8,9,12-Tetrahydroxylated Dihydroagarofuran Sesquiterpenoid from α-Santonin

The tittle compound has been synthesized successfully through the efficient andselective functional transformation of a-santonin. This procedure is the first successful approachdeveloped for synthesis of the dihydroagarofuran kind of sesquiterpenoids from the eduesmanolidesesquiterpenoid α-santonin.

Novel 2-aryl-3,4,5-trihydroxypiperidines:Synthesis and glycosidase inhibition

Three pairs of novel 2-aryl-3,4,5-trihydroxypiperidines （6-8 and their enantiomers）, the piperidine analogues of the pyrrolidine alkaloids radicamine A and radicamine B, were prepared from six- membered cyclic nitrones through a concise two-step procedure, i.e., Grignard reagent addition and deprotection. These novel polyhydroxylated piperidine iminosugars were assayed against 10 types of enzymes. Only compound 8 exhibited weak inhibition （IC50 1080 μmol/L） against β-galactosidase from rat intestinal lactases.

Concise synthesis of 1-epi-castanospermine

1-epi-Castanospermine（5） was synthesized from readily available 2,3,4,6-tetra-O-benzyl-1-deoxynojirimycin（11） in 9 steps and 21% overall yield, with selective debenzylation, Barbier reaction and reductive amination as the main reaction steps.

Synthesis and glycosidase inhibition of C-7 modified casuarine derivatives

A series of C-7 modified analogues of casuarine have been synthesized from sugar-derived nitrone and assayed against various glycosidases. Introduction of C-7 aminomethyl or amide group led to sharp decrease of the inhibitory activities.