During the past fifteen years, the experiments based on three main propositions were proceeded to carry out in our laboratory, that is, (1) Microencapsulation : The method of solvent evaporation in water or oilly phases was adopted because of its comparative simplicity in the procedure and its high reproducibility. The application of pharmacokinetic consideration to in vivo evaluation of microencapsulated drugs using beagle dogs intended for obtaining controlled-release by oral administration. The pullunan acetate phthalate microcapsules containing cefadroxil were prepared by the solvent evaporation method in liquid paraffin and showed a zero-order dissolution pattern in pH 6-7.4. (2) Rectal gel preparation : The hydrogels and xerogels were prepared by Eudispert hv. These gets have excellent staying properties in the lower part of the rectum, over a fairly long period. Eudispert hv hydrogels or xerogels containing propentfylline were tested for avoidance of the first-pass metabolism. The absolute bioavailability of propentofylline from gel preparations was almost 100%. (3) Binary vehicle for transdermal delivery : The effects of glycerides, short-chain alcohols and their binary vehicles as donor components on the skin permeation of ketoprofen across the excised hairless mouse skin were evaluated with the diffusion cell. Among single vehicles, Panasate 800 as lipophilic vehicle and ethanol as hydrophilic vehicle showed the effective permeation flux of ketoprofen. The greatest enhancement was observed in an ethanol/Panasate 800 (40/60) binary vehicle. The relationship between lipophilicity and skin permeability of 16 drugs from the ethanol/Panasate 800 (40/60) binary vehicle showed a parabolic shape with a peak at a more hydrophilic range compared with other past references.
In the biosynthetic study of griseofulvin by Penicillium urticae and microbial transformation of (-)- and (+)-dehydrogriseofulvin and their derivatives by Streptomyces cinereocrocatus excellent informations were obtained from 2H-NMR spectroscopy. In the reduction of (-)-dehydrogriseofulvin into (+)-griseofulvin by a partially purified enzyme system of S. cinereocrocatus, the origin of the 6'α-hydrogen of (+)-griseofulvin was a hydride ion donated by pro-4R-hydrogen of NADPH. In connection with the study of carcinogenesis, diethylstilbestrol (DES) was proved to disrupt microtubules in vitro. The other synthetic estrogens, E, E-dienestrol, meso-hexestrol, and dl-hexestrol were inhibitors of microtubule assembly in vitro, and induced twisted ribbon structures or ribbon-sheet-microtubules from microtubule proteins. Next, the effects of DES and its methyl ethers on the chromosome of and the cellular microtubule architecture, revealed by fluorescent anti-tubulin antibody, of Chinese hamster V79 cells were examined, and further estradiol-17β was proved to exhibit higher microtubule-disruptive activity than DES in V79 cells. Furthermore, cytoplasmic microtubules in the human breast cancer cell lines MCF-7 and MDA-MB-231, estrogen receptorpositive and -negative cell lines, respectively, were disrupted equally by estradiol-17β. Then, natural estrogens and their derivatives comprising 30 compounds in total were tested in Chinese hamster V79 cells, proving that 2-methoxyestradiol showed the strongest activity (EC50 : 2μM) to disrupt microtubules. Further, in the assay of indenestrol A, a metabolite of DES, indenestrol B and their monomethyl ethers, the 4'-methyl ether of [(-)-3S]-indenestrol B exhibited both the strongest cytotoxicity in, and greatest disruption of the cellular microtubules of V79 cells, and no correlation with the affinity for estrogen receptors was shown.
Although N-hydroxyamides (1) have been known for over a century, the chemistry of 1 is still relatively unexplored. The scope of the present review is a survey of the recent advances of the chemistry of 1 and its derivatives, particularly of new chemical reactions having synthetic utility in organic synthesis developed mainly in our laboratory. The review is divided into two sections. The first section described great utility of divalent positively-charged nitrogen species generated from 1 in synthesis. Electrophilic intramolecular cyclization with an acylnitrenium ion generated from an N-methoxy- or an N-allyloxy-N-chloroamide with anhydrous zinc acetate in nitromethane gave an N-methoxy- or an N-allyloxy nitrogen heterocyclic compound, deprotection of which led to formation of the corresponding N-hydroxy compound. Treatment of an N-hydroxy- or an N-methoxy-N-arylamide and the corresponding lactam with various reagents results in removal of the hydroxy or methoxy function and introduction of nucleophiles at the ortho or para position of the aromatic ring. These methodologies were successfully applied by us for the synthesis of the alkaloid, eupolauramine and for new oxindoles related to the alkaloid, gelsemine, by others. The second section described great utility of N-alkoxyimidoyl halides (2) synthesized from 1. Compounds 2 were readily transformed to other functions such as aldehydes, cyanides, and oximes. This methodology was successfully applied to the synthesis of ω-N-hydroxy-α-amino acids in optically pure form which were the key intermediates for the synthesis of hydroxamate-containing siderophores.
Asymmetric reduction of acetophenone (FK3311 : 1) and ethyl phenylglyoxylate (7) with various chiral reducing agents was investigated in an attempt to synthesize both optical isomers of the two metabolites (2 and 5) of 1. The treatment of 1 with 3, 3-diphenyl-1-methyltetrahydro-1H, 3H-pyrrolo[1, 2-c]-[1, 3, 2]-oxazaborolidine-borane complex (reductants B, C) gave chiral alcohol 2 in a high optical purity. On the other hand, reduction of 7 by B-chlorodiisopinocamphenylborane (reductants E, F) gave the best result among the tested reagents. Each isomer of 2 and 5 was examined for in vitro activity to inhibit zymosan-induced prostaglandine E2 production, adjuvant-induced arthritis for antiinflammatory activity, and acetic acid-induced writhing for analgesic activity in comparison with the racemic mixture.
Seratrodast [(±)-7-(3, 5, 6-trimethyl-1, 4-benzoquinon-2-yl)-7-phenylheptan-oic acid], a thromboxane A2 antagonist, developed as an antiasthmatic, has two crystalline forms, form I and form II. Form I was a stable form and form II was metastable form since the crystalline form was transformed into form I by heating. By differential scanning calorimetry, form I showed only an endothermic peak at about 130°C with melting but form II additionally showed an exothermic peak at about 90°C. This exothermic peak was the transition point of form II to form I. A method for the determination of the ratio of form II in seratrodast was established from the ratio of the exothermic calorific value to the endothermic calorific value on the differential scanning calorimetric curve. The transition of form II to form I appeared to follow the zero-order mechanism. The activation energy of this transition was 270kJ/mol calculated from the Arrhenius plots.
A significant difference in the bond distances or angles and short contacts between the two adjacent isoalloxazine (IA) rings in the riboflavin tetracarboxylate crystal are attributable to the nonbonded interaction. The perturbation of the electronic state in the IA ring accompanied by the elimination of the protic solvent well explains an occurrence of charge transfer (CT) interaction. This inference is supported by the fact that the IA rings are overlapping face to tail in the concentrated solution and the solvation takes place at the IA ring. In the frontier molecular orbital theory, it is possible to consider that the interaction occurs between the HOMO of the solvent-eliminated IA, which acts as a donor, and the LUMO of the solvated IA, which behaves as an accepter. The effect of the CT interaction on the stacking interaction can be measured quantitatively as the red shift or quenching in the reflection and the emission spectra and the signal in the ESR. It is certain that this report gives an important clue about the interrelation between the CT interaction and the hydrophobic environment in the stacking interaction.