Suppression of bitterness and improvement of palatability of commercial prednisolone powder

The aim of the study was to suppress the bitterness and improve the palatability of pediatric prednisolone powder (PP) by the addition of simple sucrose syrup (SS) and various beverages and foods. Bitterness suppression was evaluated using the human gustatory sensory test. The suppression of the bitterness and improvement of palatability of PP by addition of SS solutions was investigated using standard taste substances: sucrose for sweetness, tartaric acid for sourness, and sodium chloride as saltiness. Dilution with SS solutions of up to 50% (w/w) was successful in bitterness-suppression and improvement of palatability, but at 80% (w/w) SS, the palatability of the diluted solution was reduced. The kinematic viscosities of SS solutions were therefore evaluated using the Uberorde viscosity meter, to see whether the high viscosity of the more concentrated solutions was responsible for the reduced palatability. The kinematic viscosity of the 80% SS was 16.60 mm(2)/s. Judging from above information, the palatability might become worse when the kinematic viscosity of syrup exceeded 15 mm(2)/s. Finally, the ability of various beverages and foods with low viscosity to suppress the bitterness and improve the palatability of PP were examined. The additions of orange juice or a carbonated lemon drink to simple syrup solution were most effective in suppressing bitterness and improving palatability of PP.     

Catenane gel: synthesis of high molecular weight poly[2]catenanes by Sonogashira coupling polymerization

A first catenane polymer gel was obtained by Sonogashira coupling reaction of diiodo[2]catenane and 4,4′-diethynylbiphenyl. Because of the linearity and rigidity of the ethynylene group formed in the coupling reaction, the formation of undesired cyclic dimer was inhibited, and a very high molecular weight (M_n > 2.3 × 10⁵) poly[2]catenane was synthesized. The polymer was gelated without any chemical cross-linkage and swelled in DMF.     

Control of conformer population and product selectivity and stereoselectivity in competitive photocyclization/rearrangement of chiral donor-acceptor dyad

The conformer population and the relative excitation efficiency of each conformer, assessed by theoretical and experimental examinations, enabled us to precisely control the chemo- and diastereoselectivities of the competitive photocyclization/rearrangement reaction of a chiral donor-acceptor (D/A) dyad by irradiation wavelength, solvent polarity, and reaction temperature. Manipulating the ground- and excited-state conformer equilibria is essential for critically controlling the intramolecular D/A system, in sharp contrast to the rather divergent excited species involved in relevant intermolecular systems.     

Use of the oxazole-olefin diels-alder reaction in the total synthesis of the monoterpene alkaloids (-)-plectrodorine and (+)-oxerine

A full account of the total synthesis of two monoterpene alkaloids, (-)-plectrodorine [(-)-1] and (+)-oxerine [(+)-3], is presented. The key steps involved are the formation of the oxazole alcohol 10 from the gamma-butyrolactone 9 and the intramolecular Diels-Alder reaction of the oxazole-olefins 13a, b. Since the sign of specific rotation for the synthetic (+)-3 was different from that reported for natural oxerine, the absolute configuration of this alkaloid is not yet fully understood.