Shwu-Chen Tsay

Thermal- and photo-induced transformations of N-aryl-N-nitrosohydroxylamine ammonium salts to azoxy compounds

Heating of an ethanolic solution containing N-aryl-N-nitrosohydroxylamine ammonium salts at 78 °C produced the desired azoxy compounds in 80–93% yields. Furthermore, irradiation with UV light (λ≥300 nm) of ethanolic solutions of those ammonium salts at room temperature also provided the desired azoxy compounds in 51–72% yields.

New Triruthenium Clusters as Photoinduced DNA-binding and Cleaving Agents¶

Abstract 1-Hydroxybenzotriazole and 1-hydroxypyridine-2-thione were incorporated as ligands with the cluster Ru3(CO)10(NCMe)2 to give [(μ-H)Ru3(CO)10(μ2-2,3-&eegr;2-NNN(O)C6H4)] and [(μ-H)Ru3(CO)9(μ2-&eegr;1u2009:u2009&eegr;2-C5H4N(O)S)], respectively. Irradiation of these two new triruthenium metal clusters individually with 350 nm UV light in a phosphate buffer (pH 6.0) containing form I DNA resulted in single-strand cleavage. Cluster [(μ-H)Ru3(CO)10(μ2-2,3-&eegr;2-NNN(O)C6H4)] was also found to bind to calf thymus DNA upon UV irradiation.

Photochemical cleavage of single- and double-stranded oligonucleotides by 3-(p-tolylamino)-1,5-azulenequinone

Irradiation, with 350 nm UV light, of specially designed and synthesized single- and double-stranded oligodeoxyribonucleotides in the presence of 3-(p-tolylamino)-1,5-azulenequinone produced fragments resulting from the cleavage at the deoxyguanosine residue only. The cleaving efficiency was greater for a single strand than a double helix. The efficiency was increased for a less stable double helix, or while the deoxyguanosine residue therein was located at a bulge, at a hairpin loop, or towards the end of the helix.

Direct synthesis of diallyl sulfides from allyl alcohols and hexamethyldisilathiane

Abstract Diallyl sulfides were obtained in 60–90% yields by reaction of various allyl alcohols (1.0 equiv) with hexamethyldisilathiane (≈0.55 equiv) in CH2Cl2 at room temperature in the presence of BF3·OEt2 (0.8–1.1 equiv).

Synthesis and immunofluorescence assay of a new biotinylated paclitaxel

7-(5-Biotinylamidopropanoyl)paclitaxel was synthesised by chemical methods; its immunofluorescence assay and the cell uptake experiments were performed by use of human leukemia U937 cells. The results indicate that paclitaxel is arresting cell cycle at the G(2)M phase only.

Single-strand cleavage of DNA with site-specificity by photolysis of azulenequinones

Abstract Single-strand cleavage of DNA in a phosphate buffer at pH 6.0 was accomplished by photolysis of various 1,5- and 1,7-azulenequinones with 350-nm UV light; results from the analysis of a 32 P-end-labeled DNA fragment obtained by gel electrophoresis indicate the predominant cleavage occurring at the guanine residue.

Different roles of trifluoromethanesulfonyl chloride in the construction of heterocycles fused with β-lactams

Abstract The cis-configurated tricyclic O3-isooxacepham 5 and bicyclic isopenam 11 were synthesized. The key step for the preparation of 5 involves chlorination of the corresponding carbanion of 3 with CF3SO2Cl followed by an internal alkylation. The biologically active isopenam 11 was synthesized from thio-S-ester 6 via intermediate 9. The key step involves chlorination of the thiol moiety in monocyclic β-lactam 7 by CF3SO2Cl followed by an internal cyclization.

Concept of Counterattack Reagents: Intramolecular Counterattack Strategy in the Synthesis of Biologically Active Isopenams

Potent antimicrobial activities or promising β-lactamase inhibitory properties were found for isopenams that were synthesized by an “intramolecular counterattack” strategy (see diagram).

Silicon-controlled oxidation of enol acetates to enones by electrochemical method

Abstract Anodic oxidation of β-silylcycloalkanone enol acetates 1a-d in glacial acetic acid containing tetraethylammonium p -toluenesulfonate afforded α,β-unsaturated β-silylcycloalkenones 2a-d exclusively in 81–95% yields. The silyl group in 1a-d directed the oxidation under electrochemical conditions.

Synthesis and biological evaluation of an electronically activated isooxacephem

New isooxacephem (+/-)-3-ethyl 2-hydrogen (6RS,7RS)-8-oxo-7-(phenylacetamido)-4-oxa-1-azabicyclo [4.2.0]oct-2-ene-2, 3-dicarboxylate (8) was synthesized from (+/-)-dibenzyl 2-[cis-2-oxo-3-(phenylacetamido)-4-styryl-1-azetidinyl]-2-[t- butyldimethylsiloxy(methoxycarbonyl)methyl]malonate (1) in six steps. This bicyclic beta-lactam was found to possess notable biological activities against several pathogenic microorganisms in vitro, including Staphylococcus aureus 95, S. aureus FDA 209P, Escherichia coli ATCC 39188, Salmonella typhi O-901, Pseudomonas aeruginosa 18S-H, P. aeruginosa 1101-75, and Klebsiella pneumoniae NCTC 418. The electronic activation of the beta-lactam moiety by an ester group plays a prominent role in the biological activity of this novel isooxacephem.