Binaphthyldiamino salen-type Zn, Cu, and Co complexes can efficiently catalyze reactions of epoxides with carbon dioxide in the presence of various catalytic amounts of organic bases. The simplest binaphthyldiamino salen-type Zn complex gave the five-membered cyclic carbonate 2 in excellent yield in the presence of triethylamine. A Lewis acid and Lewis base cocatalyzed mechanism is proposed.

Binaphthyldiamino, ethyldiamino and cyclohexyldiamino Schiff bases can catalyze the reaction of epoxides with carbon dioxide in the presence of catalytic amounts of various organic bases to give the corresponding cyclic carbonates in high yields. The simplest binaphthyldiamino Schiff base, derived from the reaction of binaphthyldiamine with salicylaldehyde, gave the highest yield of cyclic carbonate. This catalytic system can be further simplified by use of a phenol instead of the Schiff base to give the corresponding cyclic carbonates in high yields as well. Mechanistic insights were obtained based on a deuterium labeling experiment. The reaction of aziridines with CO2 and epoxide with CS2 were also examined under the same reaction conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Three conjugates based on dendrimer PAMAM generation five were synthesized and radiolabeled successfully. To investigate their tumor targeting, the in vitro and in vivo stability, cell uptake, in vivo biodistribution, and micro-SPECT imaging were evaluated, respectively. The conjugate of (99m)Tc labeled PEGylated dendrimer PAMAM folic acid conjugate ((99m)Tc-G5-Ac-pegFA-DTPA) shows much higher uptake in KB cancer cells and accumulated more in the tumor area than that of the other two conjugates. The uptake in KB cells depends on the incubation time. The results of in vivo biodistribution agree with the data obtained from micro-SPECT imaging. These studies show that PEGylation of PAMAM dendrimer folic acid conjugate improves the tumor targeting. Folate-conjugated dendrimer maybe developed to be potential radiopharmaceuticals and targeted drug delivery systems.

Without protection: α‐Keto aziridines have been formed in a novel amine‐promoted direct aziridination of chalcones using an aminimide generated in situ from a tertiary amine and O‐mesitylenesulfonylhydroxylamine (MSH) in the presence of base (see scheme). The aziridination proceeds well using a catalytic amount of the tertiary amine. Furthermore, nonracemic aziridines are obtained using a chiral amine.

Phenol can efficiently catalyze the reactions of terminal epoxides with carbon dioxide in the presence of catalytic amounts of various organic bases such as 4-dimethylaminopyridine (DMAP), pyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, and triethylamine to give the corresponding five-membered cyclic carbonate in high yields (initial pressure 3.57 MPa; reaction temperature 120 8C). p-Methoxyphenol with DMAP is the best combination to give the cyclic carbonate in the highest yield.

The purD gene of Escherichia coli encoding the enzyme glycinamide ribonucleotide (GAR) synthetase, which catalyzes the conversion of phosphoribosylamine (PRA), glycine, and MgATP to glycinamide ribonucleotide, MgADP, and Pi, has been cloned and sequenced. The protein, as deduced by the structural gene sequence, contains 430 amino acids and has a calculated Mr of 45,945. Construction of an overproducing strain behind a lambda pL promoter allowed a 4-fold purification of the protein to homogeneity. N-Terminal sequence analysis and comparison of the sequence with those of other GAR synthetases confirm the amino acid sequence deduced from the gene sequence. Initial velocity studies and product and dead-end inhibition studies are most consistent with a sequential ordered mechanism of substrate binding and product release in which PRA binds first followed by MgATP and then glycine; Pi leaves first, followed by loss of MgADP and finally GAR. Incubation of [18O]glycine, ATP, and PRA results in quantitative transfer of the 18O to Pi. GAR synthetase is very specific for its substrate glycine.

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The reactions of propargylamine derivatives with carbon dioxide and carbon disulfide have been systematically examined in the presence of transition-metal catalysts. Pd(OAc)(2) is the best catalyst for the formation of the corresponding oxazolidinones. In addition, we found that, in the reaction of propargylamine with carbon dioxide catalyzed by palladium(0) metal catalyst in toluene, both oxazolidinone 1 and imidazolidinone 2 could be obtained under mild reaction conditions at the same time. The reaction of 1 with primary and secondary amines has been examined. A plausible reaction mechanism for the formation of 2 was proposed. In addition, in this paper, we first disclosed the ligand's effect on this reaction. Using PBu(t)(3) as a ligand with Pd(2)(dba)(3), 1 was exclusively formed in 90% yield.