Changeable reactivity of ketyl radicals derived from 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones depending on electron transfer conditions employed

Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols.     

Poly(N-n-butylitaconimide). Preparation and characterization

Poly(N-n-butylitaconimide) was prepared by radical polymerization in benzene and in bulk at 60°C and was subsequently fractionated at 30°C with benzene and methanol as solvent and nonsolvent, respectively. Relationships between molecular weight and intrinsic viscosity (Mark-Houwink-Sakurada equations) in tetrahydrofuran, benzene, and toluene at 30°C are established. From the Burchard-Stockmayer-Fixman plot, the characteristic ratio of this polymer is determined, and local chain conformation is discussed in relation to the termination process in radical polymerization. © 1993 John Wiley & Sons, Inc.     

Reaction profiles and substituent effects for the reduction of carbonyl compounds with monomer and dimer simple metal hydride reagents

Reaction profiles and energetics for the reactions of substituted benzaldehydes with a series of different simple metal hydrides (BH(3), BMeH(2), BMe(2)H, AlH(3), and AlMe(2)H) are examined computationally. B3LYP/6-31G optimizations and MP2/6-311G single point energy calculations revealed that the Al reagents are more reactive than B reagents. Replacement of H with Me on BH(3) or AlH(3) makes the reduction transition state (TS) less stable. Accordingly the overall reactivity is in the order AlH(3) > AlMe(2)H > BH(3) > BMe(2)H. The Hammett rho value for substituted benzaldehydes (BAs) is negative for the initial complex formation and positive for the hydride-transfer step. The size and the sign of the apparent rho value depend on the relative stabilities of the separated reactants and the complex. The TS structures vary according to the Hammond postulate for substituted BAs and the variation is reflected in carbonyl-carbon and aldehyde-deuterium isotope effects. Comparison of the reaction profiles of the monomer and dimer reagents reveals that the real reacting species is the monomer in the gas phase for BH(3) but the dimer for BMe(2)H.     

Chemistry of renieramycins. Part 7: Renieramycins T and U, novel renieramycin-ecteinascidin hybrid marine natural products from Thai sponge Xestospongia sp.

Two new bistetrahydroisoquinoline marine natural products, renieramycins T (1) and U (2), were isolated from the Thai blue sponge Xestospongia sp. and their structures were elucidated by comparing spectral data with those of renieramycin M (3a) and ecteinascidin 770 (4a). These compounds are the first reported examples of novel ecteinascidin-renieramycin hybrid natural products. Renieramycin T (1) showed strong cytotoxicity to several human cancer cell lines, its IC₅₀ values ranging from 4.7 to 98 nM.     

A Pair of Families of Non-isomorphic Group Association Schemes with the same Parameters

We show that for the split and non-split extensions ofFq²bySL (2, q) (q =  2^e,e  ≥  3), the group association schemes have the same parameters but are not isomorphic. For the split and non-split extensions ofFq²by the standard Borel subgroup of SL(2,q ) (q =  2^e, e ≥  3), the group association schemes are shown to be isomorphic.     

Assay of Angiotensin I-converting Enzyme-inhibiting Activity Based on the Detection of 3-Hydroxybutyrate with Water-soluble Tetrazolium Salt.

A newly synthesized substrate, 3-hydroxybutyrylglycyl-glycyl-glycine (3HB-GGG), was applied to the assay of ACE-inhibiting activity to overcome the smaller selectivity and sensitivity of the conventional method. In this study, an ACE-inhibiting assay was improved by the use of a water-soluble tetrazolium salt, 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate sodium salt (WST-1), for the detection of 3-hydroxybutyrate, derived from 3HB-GGG. The optimized conditions were as follows: 0.333 mM NAD(+), 0.333 mM WST-1, 0.1 mM EDTA, 0.633 U ml(-1) diaphorase, and 0.700 U ml(-1) 3-hydroxybutyrate dehydrogenase. The developed assay was efficiently applicable to evaluate the ACE-inhibiting activity of practical ACE inhibitors.     

Synthesis and Application of a Bidentate Ligand Based on Decafluoro‐3‐phenyl‐3‐pentanol: Steric Effect of Pentafluoroethyl Groups on the Stereomutation of O‐Equatorial C‐Apical Spirophosphoranes

1,1,1,2,2,4,4,5,5,5‐Decafluoro‐3‐phenyl‐3‐pentanol was prepared by a Cannizzaro‐type disproportionation reaction, and the dimetallated compound was used as a bidentate ligand, which is bulkier than the Martin ligand (1,1,1,3,3,3‐hexafluoro‐2‐phenyl‐2‐propanol). A P? H spirophosphorane was synthesized by utilizing the new bidentate ligand, and the structure of the product was essentially the same as that of the P? H phosphorane with Martin ligands. Phosphoranes that exhibit reversed apicophilicity (O‐equatorial) were also synthesized and could be converted into the corresponding stable stereoisomers (O‐apical). The crystal structures of O‐equatorial phosphoranes and the O‐apical isomers were slightly affected by the steric repulsion of pentafluoroethyl groups. Kinetic measurements revealed that the stereomutation of O‐equatorial methylphosphorane to the O‐apical isomer was slowed. The activation enthalpy for the stereomutation of the former to the latter was higher than that of the phosphorane with Martin ligands by 5.1 kcal mol^?1.     

An iridoid glucoside dimer and a non-glycosidic iridoid from the leaves of Lasianthus wallichii

A new iridoid glucoside dimer (1) and a non-glycosidic iridoid (2) was isolated together with the known compounds, asperuloside (3), paederoside (4), daphylloside (5), citroside A (6) and benzyl 6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranoside (7), from the leaves of Lasianthus wallichii. The structures of the new compounds were elucidated by spectroscopic and chemical evidence.     

Simultaneous determination of creatinine, creatine, and UV-absorbing amino acids using dual-mode gradient low-capacity cation-exchange chromatography

A simple and versatile cation-exchange chromatography technique for the simultaneous determination of urinary creatinine (Cre), creatine (Crn), methionine (Met), tyrosine (Tyr), phenylalanine (Phe), histidine (His), and tryptophan (Trp) was developed. A novel low-capacity cation-exchange column packed with a newly developed sulfoacylated hypercross-linked macroreticular polystyrene-divinylbenzene resin, referred to as TMR-A/75 (capacity: 75 microequiv/column), was successfully used with a binary dual-mode gradient eluting system. Two solvents, (A) 25 mM phosphoric acid-methanol (30:70, v/v) and (B) 25 mM disodium hydrogenphosphate-methanol (30:70, v/v) were pumped through the column by programming solvent delivery ratios as 0 to 5 min: A-B (55:45, pH 3.6); 5-21 min: A-B (49:51, pH 5.3); and 21-35 min: A-B (55:45, pH 3.6). The flow rate was simultaneously time-programmed to be 0.6 mL/min from 0 to 19 min and to be 1.0 mL/min from 19 to 35 min. This eluting system could permit the use of the UV detection at 210 nm. The analytes, Crn, Met, Tyr, His, Cre, Phe, and Trp, were well separated in this order in 27 min with minimum resolution of approximately 2, and the cycle time was about 35 min. Retention time of each analyte was very reproducible with relative standard deviations (RSDs) between 0.05 and 0.38% (n = 5). The peak area responses were also reproducible with RSDs between 0.74 and 2.24% (n = 5). Calibration lines based on area data were linear from 1 to 1000 microM with r2 values of 0.9998 (Crn), 0.9998 (Met), 0.9999 (Tyr), 0.9999 (His), 1.0000 (Cre), 1.0000 (Phe), and 0.9999 (Trp). The method was applicable to the screening and/or chemical diagnosis of inherited metabolic disorders such as phenylketonuria (PKU), tyrosinemia, and Lowe syndrome. The creatinine ratios of diagnostic markers (microM/microM Cre) were easily determined. The Phe/Cre ratios for five urines from patients with PKU ranged from 0.162 to 0.521, and the Tyr/Cre ratio for tyrosinemia was 0.147. The ratios of Tyr/Cre, Phe/Cre, and Trp/Cre for Lowe syndrome were 0.497, 0.321, and 0.495, respectively. In contrast, the creatinine ratios for healthy newborns showed one digit lower than those for patients did. The developed method is very practical and can provide useful information and results for the clinical or biomedical researches with low analytical run costs.