Five new chromones possessing monoamine oxidase inhibitory activity from an ascomycete, Chaetomium quadrangulatum

Five novel chromones (1,4-benzopyran-4-ones), among which three are tetracyclic and one contains a sulfonyl group, have been isolated from an Ascomycete, Chaetomium quadrangulatum, as monoamine oxidase inhibitory features, and named chaetoquadrins A (1)-E (5).     

Total synthesis of flavocommelin, a component of the blue supramolecular pigment from Commelina communis, on the basis of direct 6-C-glycosylation of flavan

We succeeded in a first total synthesis of flavocommelin (1), a component of the blue supramolecular pigment, commelinin (2), from Commelina communis, by direct 6-C-glycosylation of the flavan 4 using perbenzylglucosyl fluoride 8 in the presence of MS 5 angstroms in CH2Cl2 and a catalytic amount of BF3 x Et2O. After 6-C-glycosylation of 4, oxidation with CAN to flavanone 18 and subsequent 4'-O-glycosylation, promoted with a combination of BF3 x Et2O and DTBMP, afforded diglucosylflavanone 20. DDQ oxidation of 20 and deprotection successively gave 1.     

Effects of the water content on the growth rate of AgCl nanoparticles in a reversed micelle system

The effects of water content on the growth rate and the final particle size of AgCl nanoparticles in a reversed micelle (RM) system of polyoxyethylene (6) nonylphenyl ether (NP-6)/water/cyclohexane were investigated using a double-jet technique, in which RM solutions of AgNO(3) and KCl were added concurrently to a RM solution containing the excess concentration of chloride ion. As a result, the particle growth rate and the final particle size at a constant Rw ( identical with[water]/[surfactant]) below 5 were found to be in excellent agreement with our theoretical prediction based on a dynamic Ostwald ripening mechanism governed by the overall solubility of the solid and the diffusivity of the reversed micelles, whereas the final particle size was far beyond the size of the water pool of a reversed micelle. Thus, the dramatic reduction of the particle size in the RM system can be explained by the drastic reduction of the overall solubility of the solid and the small diffusivity of the bulky reversed micelles as a carrier of silver ion, and not by the size of the water pool of a reversed micelle as conventionally explained. Some additional contribution of a coagulation process was also suggested in a high Rw range above 5. Significant coagulation of AgCl particles was observed in a RM system with AOT in place of NP-6 even under the standard conditions for the NP-6 system.     

Total synthesis of the hallucinogenic neoclerodane diterpenoid salvinorin A

Total synthesis of salvinorin A (1), a neoclerodane diterpenoid having the most potent hallucinogenic activity and a selective kappa-opioid agonist, was completed in 20 steps starting from enantiomerically pure hydroxy-Wieland-Miescher ketone 5.     

Elution behavior of diaminopimelic acid and related diamino acids using the advanced Marfey's method

The advanced Marfey's method consists of a chromatography technique for the separation of amino acids into each enantiomer by derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-leucinamide (L-FDLA), and a detection method using liquid chromatography/mass spectrometry (LC/MS) which can determine the non-empirically the absolute configuration of various amino acids including the non-protein ones. However, this method has not been applied to the determination of the absolute configuration of an amino acid with a "meso" configuration such as diaminopimelic acid (A2pm). In the present study, this method was successfully applied to determine the absolute configurations of diaminosuccinic acid (DAS), A2pm, cystine (Cys), selenocystine (SeCys) and homocystine (HomoCys) using a racemization procedure and the DL-FDLA method, and the resulting elution behavior was summarized as follows: (1) the LL- and meso-isomers were eluted prior to the DD-isomer except for one case; (2) the LL- and meso-isomers are closely eluted and the elution was occasionally reversed; (3) the retention time for both the L- and D-derivatives of the meso-isomer was not changed; (4) the complementary use of the two solvent systems using CH3CN and MeOH was effective to obtain a chromatogram with a high resolution; (5) the abnormality, such as the elution order and peak shape, was observed in the elution behavior of DAS.     

Successive determination of urinary protein and glucose using spectrophotometric sequential injection method

A new sequential injection (SI) system with spectrophotometric detections has been developed for successive determination of protein and glucose. The protein assay is based on ion-association of protein with tetrabromophenolphthalein ethyl ester (TBPE) in the presence of Triton X-100 at pH 3.2. The blue product is monitored for absorbance at 607 nm. For glucose, hydrogen peroxide, generated by the oxidation of glucose in the presence of glucose oxidase immobilized on glass beads packed in a minicolumn, is monitored using iron-catalyzed oxidation reaction of p-anisidine to form a red colored product (520 nm). The SI procedure takes advantage in performing the protein assay during the incubation period for glucose oxidation. Linear ranges were up to 10 mg dL⁻¹ human serum albumin (HSA) with a limit of detection (LOD) (3σ) of 0.3 mg dL⁻¹, and up to 12.5 mg dL⁻¹ glucose with LOD of 0.08 mg dL⁻¹. R.S.D.s (n = 11) were 2.7% and 2.5% (for 1 mg dL⁻¹ and 5 mg dL⁻¹ HSA) and 1.4% (9 mg dL⁻¹ glucose). Sample throughput for the whole assay of both protein and glucose is 6 h⁻¹. The automated system has been demonstrated for the successive assay of protein and glucose in urine samples taken from diabetic disease patients, with good agreement with the other methods. This developed SI system is an alternative automation for screening for diabetic diagnosis.     

Elongational flow opto-rheometry for polymer melts

Polymer melt elongation is one of the most important procedures in polymer processing. To understand its molecular mechanisms, we constructed an elongational flow opto-rheometer (EFOR) in which a high precision birefringence apparatus of reflection-double path type was installed into a Meissner's new elongational rheometer of a gas cushion type (commercialized as RME from Rheometric Scientific) just by mounting a small reflecting mirror at the center of the RME's sample supporting table. The EFOR enabled us to achieve simultaneous measurements of tensile stress (t) and birefringence n(t) as a function of time t under a given constant strain rate within the range of 0.001 to 1.0s^–1. (t) can be monitored upto the maximum Hencky strain (t) of 7 as attained, in principle, with RME, while the measurable range of the phase difference in the birefringence was 0 to 250 (0 to 79 100 nm for He-Ne laser light) within the accuracy of ±0.1 (±31.6 nm) up to (t) 4. The performance was tested on an anionically polymerized polystyrene (PS) and a low density polyethylene (LDPE). For both polymers (t) first followed the linear viscoelasticity rule in that the elongational viscosity, , is three times the steady shear viscosity, 3 _o(t), at low shear rate , but the _E (t) tended to deviate upward after a certain Hencky strain was attained. The birefringence n(t) was a function of both Hencky strain and strain rate in such a way that the stress-optical law holds with the stress-optical coefficient C(t) = n(t)/(t) being equal to the ones reported from shear flow experiments. Interestingly, however, for PS elongated at low strain rates the C(t) vs (t) relation exhibited a strong nonlinearity as soon as (t) reached steady state. This implies that the tensile stress reaches the steady state but the birefringence continues to increase in the low strain-rate elongation. For the PS melt elongated at high strain rates, on the other hand, C(t) was nearly a constant in the entire range observed. For LDPE with long-chain branchings, (t) exhibited tendency of strain-induced hardening after certain critical strain, but C(t) was nearly a constant in the entire range of (t) observed.     

Enzymatic synthesis of (-)- and (+)-acetoxyhexamides and (-)- and (+)-hydroxyhexamides.

The enantioselective hydrolysis of (+/-)-4-(1-acetoxyethyl)-N-(cyclohexylcarbamoyl)-benzenesulfona mides 3 with lipase Amano P from Pseudomonas sp. in a water-saturated solvent gave (R)-4-(1-hydroxyethyl)-N-(cyclohexylcarbamoyl)benzenesulfonamide 2 (39%, > 99% ee) and unchanged (S)-3 (50%, 62% ee). On the other hand, enantioselective esterification of (+/-)-2 with lipase Amano P in the presence of vinyl acetate provided (R)-3 (41%, > 99% ee) and unchanged (S)-2 (46%, 78% ee).     

Coprecipitation Behavior of Some Metals with Chitosan and Their Determination by Graphite Furnace Atomic Absorption Spectrometry

Chitosan is derived from chitin by deacetylation. Chitosan forms a complex with metal ions and is soluble an organic acid. The metal ions were concentrated in the precipitates of chitosan when the sample solution containing metal ions was adjusted to neutral after the chitosan solution was added. These properties are applied to the preconcentration of metal ions in water samples and their determination by graphite furnace atomic absorption spectrometry. Metal ions,such as ruthenium, indium, vanadium, strontium,rhodium were collected in the chitosan precipitates.