Construction of the Skeleton of Phthalascidin, Mechanism of the Formation of the Key Tricyclic Lactam Intermediate

Phthalascidin is a structurally simplified version of Et-743, which is a potent anti-tumor marine natural product isolated from Ecteinascidia turbinata. Its antiproliferative activity is greater than that of the agents taxol, camptothecin, adriamycin, mitomycin C, cisplatin, bleomycin, and etoposide by 1-3 orders of magnitude. An elegant synthesis of Et-743 and phthalascidin has been reported by E. J. Corey and co-workers1,2. As part of our continuing program, we have also engaged in dev…     

Asymmetric Induction of Chiral 1,1''''-Bis(oxazolinyl)ferrocenes as Ligands in Metal-Catalyzed Cyclopropanation and Diels-Alder Reactions

Bis(oxazoline) ligands1 have been successfully used in a variety of metal-catalyzed asymmetric reactions, such as cyclopropanation, allylic oxidation reactions, etc; Chiral ferrocene derivatives2 have also been proved as effective ligands in numerous asymmetric reactions, for example, chiral ferrocenylphosphines exhibited high enantioselectivity for the reduction of olefins, Heck reactions and Aldol reactions of aldehydes. These results stimulated us to study the behaviour the bis(oxazoline) …     

Regioselective Addition of Silyl Enolates to α, β-Unsaturated Aldehyde and its Acetal Catalyzed by MgI_2 Etherate

In our previous letter1, we have reported the unique catalytic reactivity of MgI2 etherate 1 in the chemoselective Mukaiyama-type aldol reactions of aryl or vinyl aldehyde and aldehyde acetals with silyl enolates. Aryl or alkyl a, b-unsaturated aldehydes (and their acetals) are particularly reactive in this catalytic addition reaction due to possibly the effective activation of the electron-rich carbonyl by highly oxyphilic Lewis acidic species, i.e. IMg+, in non-coordinative media (i.e. CH…     

PRODUCTION OF LIGHT ALKENES FROM CO AND/OR CO_2 HYDROGENATION OVER K-Fe-MnO/SILICALITE-2 CATALYST

High selectivity to light alkenes can be achieved from CO and CO_2hydrogenation over K-Fe-MnO/Si-2 catalyst.The alkene selectivity isinsensitive to reaction temperature for CO hydrogenation,while apparentlyincreases for CO_2 hydrogenation with raising reaction temperature.An increasein alkene selectivity is observed for both CO and CO_2 hydrogenation with GHSVrising,While a decrease with the elevation of reaction pressure for both CO/H_2and CO_2/H_2 reaction.A two-step mechanism is suggested forCO_2 hydrogenation to form hydrocarbons,by which the variations incontributions of CO and HC as products of CO_2/H_2 reaction with change ofreaction temperature,GHSV and pressure are explained.Moreover,thecatalyst is favorable for selective production of light olefins,which can alsoconcern the slightly secondary reactions of light olefins to some extent.     

Modification of Metal Complex on the StereoselectiveHydrogenation of 2,3-Butanedione

Nanoscopic metal clusters, because of their substantial difference from metal atoms and bulk metals in size and structure, have attracted great interest especially in the field of catalysis1. It is well known that additives can markedly affect the properties of metal catalysts. The effect of metal ions has been well studied in the field of heterogeneous catalysis2. However, the study of metal complex effect is scarce. We have reported that the metal complex can considerably modulate both the a…     

Synthesis and biological evaluation of 2,4-diaminopteridine derivatives as nitric oxide synthase inhibitor

A series of novel 2,4-diamino-pteridines(9a-1)were synthesized and evaluated as inhibitors of inducible nitric oxide synthase (iNOS)in vitro.It was found that 9a,9d,9e,9h,9i and 91 showed potent inhibitory activities similar to that of methotrexate(MTX),while the activities of 9b,9c,9f,9g,9j and 9k ale stronger than MTX.     

METHANE OXIDATIVE COUPLING ON ThO_2/CaF_2CATALYST

The oxidative coupling of methane(OCM)over ThO_2/CaF_2 catalystwas investigated.The catalyst was found to be active and selective for OCMreaction.At 1153 K,the C_2~ yield was 19.9% with 61.7% C_2~ selectivityand 32.1% CH_4 conversion.XRD results indicated that F~-(?)O~(2-)exchangehappened between ThO_2 and CaF_2 phases.XPS and Raman results suggestedthat the active oxygen species were generated and suitable for OCM reactionover the catalyst.     

Synthesis of macrocyclic lactones with methoxysulfonyl side chain

Two representative macrocyclic lactones with methoxysulfonyl side chain（5a and 5b）were synthesized employing Michael addition with acrolein and ring enlargement as the key steps,starting from potassium,α-oxocycloaikylsulfonates（1）in total yields of 45 and 57%,respectively.     

The Enantiomer Separations of Allethrone and Propargyllone Using Two Long Chain Acylated b-Cyclodextrin Derivatives as CGC Capillary Stationary Phases

For high bioactivity of chiral pesticides, more and more chiral isomers are prepared by enantiomer resolution or asymmetric synthesis, and the sales of chiral pesticides continuously increase in recent years1. 1S-Allethrone I and 1S-propargyllone II are indispensable intermediates for synthesizing 1S-bioallethrin and prallethrin respectively, which are representatives of chiral pesticides. Usually, 1S enantiomers of allethrone and propargyllone are more active than their 1R enantiomers wh…     

Total Synthesis of (±)-Celaphanol A

Celaphanol A was a diterpene isolated from the stems of Celastrus stephanotifolius1, which have been the subject of continued and growing interest, due to the range of biological activities shown by many members of this family2. Some have been used in traditional medicine3 or as a stimulant4 from ancient times. In order to further study the relationship between the structure and biological activity of the diterpene compound and as an extension of diterpenoid synthesis in our laboratory5, 6, …