Two synthetic approaches to rebeccamycin

Two synthetic approaches to a new indolocarbazole antitumor antibiotic, rebeccamycin, were developed. The absolute configuration of rebeccamycin was determined by a total synthesis.     

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitor

Intravascular clot formation is an important factor in a number of cardiovascular diseases. Therefore, the prevention of blood coagulation has become a major target for new therapeutic agents. One attractive approach is the inhibition of factor Xa (FXa), which is a key enzyme in coagulation cascade responsible for the generation of thrombin by limited proteolysis of its zymogen, prothrombin. We have investigated 1-arylsulfonyl-3-piperazinone derivatives, containing a 4-(piperidino)pyridine group in place of guanidino and/or amidino groups, and discovered compound M55113 (30a: 4-[(6-Chloro-2-naphthalenyl)sulfonyl]-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]piperazinone), as a potent inhibitor of FXa (IC50=0.06 microM) with high selectivity for FXa over trypsin and thrombin.     

Resolution of enantiomers by HPLC on cellulose derivatives

Summary Various polysaccharide derivatives, particularly cellulose derivatives, were synthesized and used as chiral stationary phases for optical resolution by HPLC after being adsorbed on macroporous silica gel. Cellulose triacetate (CTA-II), which was synthesized under homogeneous conditions, showed a chiral recognition ability for many racemates. Other cellulose derivatives such as cellulose tribenzoate (OB), cellulose-trisphenylcarbamate (OC), cellulose tribenzyl ether (OE), and cellulose tricinnamate (OK) also showed unique chiral recognition. Among other polysaccharide derivatives, curdlan triacetate was also exhibited an effective chiral recognition. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Thermolysis of reactive oligo(p-phenylene sulfide) containing disulfide bond

Oligo(phenylene sulfide) (OPS) containing one disulfide bond at the end of the chain, which was obtained by the oxidative polymerization of diphenyl disulfide, had a relatively low Td_10%(temperature for 10% weight loss) of 412 °C because of degradation of the disulfide bond. But this thermal cleavage of the disulfide bond promoted the curing reaction through thiophenoxy radical formation. OPS was allowed to react with diiodobenzene at 220 °C. The thermal stability of OPS was improved through the consumption of the disulfide bond and the coupling of the chain.     

Borderline of hydrogen bonding of silanols

Two new silanols bearing very bulky silyl groups, (i-Pr₃ Si)₃SiOH and (t − BuMe₂Si)₃SiOH were prepared by peracidoxidation of their respective silanes. The X − ray crystallographic analysis revealed that (t − BuMe₂Si)₃ SiOH forms a dimeric structure with hydrogen bonding, while (i − Pr₃ Si)₃ SiOH exists as a monomer in the crystal. The effects of the size of the substituents as well as the reactivity of these silanols are discussed.     

Thermochromic and solvatochromic zinc biladienones: dynamic equilibria of a metal complex having a flexible framework sensitive to environment

Dehydration of zinc biladienone was catalyzed by zinc acetate, while the reverse reaction was catalyzed by triethylamine. The transformation can be performed thermally without catalyst, and the ratio of the hydrated form to the dehydrated form depended on the solvents: the dehydrated form is favored in CHCl₃ and CH₂Cl₂, while the hydrated form is favored in hexane, pyridine, and DMF. Kinetic studies on the thermal transformation of zinc biladienone from its hydrated blue form to the dehydrated yellow-brown form were performed in toluene and THF. The rate law was half order with respect to the zinc biladienone concentration in toluene, while first order in THF, leading to a slow transformation in concentrated solution in toluene.     

Substituent effects on the kinetics for the chemiluminescence reaction of 6-arylimidazo[1,2-a]pyrazin-3(7H)-ones (Cypridina luciferin analogues): support for the single electron transfer (SET)-oxygenation mechanism with triplet molecular oxygen

Kinetics of chemiluminescence reactions of 2-methyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c, Cypridina luciferin analogue) and substituent effects of the 6-aryl group of derivatives 1 strongly suggest that the rate-determining step is a single electron transfer from an anion derived from 1 to a triplet molecular oxygen (O₂) in the oxygenation process.     

Pyrene-azacrown ether hybrid: cation-π interaction

A pyrene-modified lariat ether was synthesized in order to observe the cation-π interaction in solution.