THE CLEAVAGE REACTION OF Mo≡Mo TRIPLE BOND.SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF[CpMo(CO)_2(N,S-C9H6NS)]·O=PPh3

The reaction of[CpMo(CO)_2]_2 with 8,8'-diquinolyl disulphide C_9H_6NSSNC_9H_6 resulted in the cleavage of Mo≡Mo triple bond to give a new nononuclear complex CpMo(CO)_2(N,S-C_9H_6NS)which was refluxed with PPh_3 in THF to form the title complex.The crystal structure of the title complex was determined by X-ray diffraction.

A novel N-N bond cleavage reaction of 4-amino-1,2,4-triazole derivatives

5-Substituted-4-animo-3-thiol-l,2,4-triazoles (1a—b) react with ortho nitrochloro-benzene or para-nitrochlorobenzene to give N—N bond cleavage products 2a—d, one structure of which (2b) has been unambiguously confirmed by an X-ray structural analysis.

Palladium-Catalyzed Intermolecular Oxidative Coupling Reactions of （Z）-Enamines with Isocyanides through Selective β-C（sp2）-H and/or C = C Bond Cleavage

Herein, two efficient palladium-catalyzed intermolecular oxidative coupling reactions of （Z）-enamines with isocyanides via selective β-C（sp2）-H and/or C=C bond cleavage have been developed, leading to controllable chemodivergent and stereoselective construction of a wide range of （E）-β-carbamoylenamine derivatives containing strong intramolecular hydrogen bonds. Furthermore, possible reaction pathways for these transfor- mations are proposed on the basis of preliminary mechanism studies.

Visible Light-Promoted Ring-Opening Alkenylation of Cyclic Hemiacetals through β-Scission of Alkoxy Radicals

The chemistry of alkoxy radicals was extensively explored during the period of 1960s to 1990s,but it has remained dormant for the past few decades.Recently,alkoxy radicals attract the attentions again,because new methods for generating alkoxy radical species have emerged.These newly developed methods are mainly based on the photolysis by visible light under mild conditions,thus allowing for new transformations of the carbon-centered radical species that are generated from theβ-scission or hydrogen abstraction of the alkoxy radicals.

Design, Synthesis and Application of a Robust d_(3)-Methyithiolating Reagent

A deuterated methylthiolating reagent with a broad spectrum,designated as DMTp,has been ingeniously formulated.This new reagent can be produced with high efficiency through the simple combination of commercially available methyl 3-thiopropanoate and CD_(3)l.This novel SCD_(3) reagent exhibits excellent reactivity with electrophiles such as alkyl iodides,benzyl chlorides,aryl halides(l,Br)and aryl triflates,resulting in high levels of deuterium content(99%D).Representative deuterated methylthiolated biomolecules,such as Sulfoxaflor,havebeen synthesizedforuse in pharmaceutical discoveryand development.

The Promiscuous Activity of the Radical SAM Enzyme NosL toward Two Unnatural Substrates

The radical S-adenosyImethionine(SAM)enzyme NosL catalyzes the conversion of L-tryptophan((-Trp,1)to 3-methyl-2-indolic acid(MIA,2),a key in termediate in the biosynthesis of the peptide an tibiotic no siheptide.Previous study showed that this remarkable recombination reaction starts from the cleavage of the Cα-COO^(-) bond to result in a·CO_(2)^(-) radical migration.In contrast to the radical SAM tyrosine lyases,NosL appears unable to cleave the Cα-Cβ bond,which is intrinsically more favorable to be cleaved than the Cα-COO^(-) bond.In this study,we investigate the NosL activity with tryptamine(11)and tryptophol(12),two L-Trp analogues lacking a carboxylate moiety.We showed that NosL cleaves the C1-C2 bond of these two substrates to produce 3-methylindole(7),suggesting that the enzyme can still catalyze a β-scission when the carboxyl group of Trp is absent.We also showed the enzyme exhibits a promiscuous activity,initiating the reaction by abstracting hydrogen atoms from two different sites to produce two sets of products.

Activity identification of chimeric anti-caspase-3 mRNA hammerhead ribozyme in vitro and in vivo

To study the expression activity of various vectors containing anti-caspase-3 ribozyme cassettes in vivo, and to further study the role of caspas-3 in the apoptotic pathway, we constructed anti-caspase-3 hammerhead ribozyme embedded into the human snRNA U6, and detected the activity of the ribozyme in vitro and in vivo. Meanwhile we compared it with the self-cleaving hammerhead ribozymes that we previously studied, and with the general ribozyme, cloned into RNA polymerase II expression systems. The results showed that the three ribozymes, p1.5RZ107, pRZ107 and pU6RZ107 had the correct structure, and that they could cleave caspase-3 mRNA exactly to produce two fragments: 143nt/553nt. p1.5RZ107 has the highest cleavage efficiency in vitro, almost 80%. However, the U6 chimeric ribozyme, pU6RZ107, has the highest cleavage activity in vivo, almost to 65%, though it has lower cleavage activity in vitro. The cleavage results demonstrated that the pU6RZ107, the U6 chimeric ribozyme, could more efficiently express and downregulate the level of caspase-3 in vivo, and the ribozyme could provide an alternative approach to the research into the mechanism of apoptosis and human gene therapy also.

Enantioselective synthesis of two key intermediates for leukotrienes A_4 and B_4

Leukotrienes, arachidonic acid derived metabolites of great biological signifi-cance, are present in tissue at extremely low concentrations, so that experimentalquaatities are only accessible by chemical synthesis. In various synthetic routes,[S,S-（E）]-3-（hydroxymethyl） oxiranebutanoic acid methyl ester （1） and （S）-5-（ben-zoyloxy）-6-oxohexanoic acid methyl ester （2） have been frequently used as the C-Cfragment of LTA3 and the C-Cfragment of LTB4, respectively. （Scheme1）