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Two syntheses of some optically active 2‐benzyl‐2,3‐dihydro‐4H‐benzopyrans and benzopyran‐4‐ones are presented. An asymmetric synthesis starting from D‐ and L‐phenylalanine was used to provide both enantiomers of 2‐benzyl‐6‐(methoxycarbonyl)‐2,3‐dihydro‐4H‐benzopyran‐4‐one 19. Phenylalanine was diazotized in aqueous sulfuric acid to 2‐hydroxy‐3‐phenylpropionic acid 6 which was converted in four steps to 1‐bromo‐2‐(4‐methoxycarbonylphenoxy)‐3‐phenylpropane 11. (4R,S)‐Benzamido‐2‐benzyl‐2,3‐dihydro‐6‐(methoxycarbonyl)‐4H‐1‐benzopyran‐4‐carboxylic acid 16 was prepared from 11 by amidoalkylation with α‐hydroxyhippuric acid in methanesulfonic acid solution followed by spiroalkylation to (4R,S)‐2‐benzyl‐2,3‐dihydro‐6‐(methoxycarbonyl)spiro[4H‐benzopyran‐4,4′‐2′‐phenyloxazolidin]‐5′‐one 15. After the phenyloxazolidin‐5‐one 15 was hydrolyzed to the spirobenzamido carboxylic acid 16, oxidative decarboxylation with sodium hypochlorite yielded optically active 2‐benzyl‐6‐(methoxycarbonyl)‐2,3‐dihydro‐4H‐benzopyran‐4‐one 19. The ketone in 19 was reduced by hydrogenation over palladium on carbon to a methylene group and the ester was converted to the aldehyde to give both isomers of the desired intermediate 2‐benzyl‐6‐(formyl)‐2,3‐dihydro‐4H‐benzopyran 25. The second synthesis relied on an enzymatic hydrolysis of ethyl 2,3‐dihydrobenzopyran‐2‐carboxylate 27 with the lipase from P. fluorescens to provide the desired 2R‐ester. The ester group in (R)‐27 was converted to the triflate (R)‐29. Displacement of the triflate group with phenylmagnesium bromide and cuprous bromide as catalyst gave 2R‐benzyl‐2,3‐dihydro‐4H‐benzopyran (R)‐30. Formylation of (R)‐30 provided 2R‐benzyl‐6‐(formyl)‐2,3‐dihydro‐4H‐benzopyran (R)‐25 identical with that from the first synthesis. These optically active intermediates are used in the preparation of the hypoglycemic agent englitazone.

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The double layer theory of Otto Stern may be briefly summarized as follows (7, 12,14). The theory of Helmholtz gives values for the capacity of the double layer which agree approximately with those obtained from electrocapillary experiments. However, owing to kinetic heat motion, the double layer ions facing the liquid cannot have the distribution postulated by Helmholtz. On the other hand, Gouy's (6) theory, which is based on the existence of a diffuse double layer, gives values for the capacity which are far too great. Stern develops his concept of the double layer in this manner: 311

An efficient synthesis of the PDE IV inhibitor, 9H-cyclopentyl-7-ethyl-3-(thiophen-2-yl)-pyrazolo[3,4-c]-1,2,4-triazolo-5,6-dihydro-[4,3-a]pyridine 1 is described. Starting from commercially available γ-caprolactone, the synthesis was carried out in 10 steps. Key transformations were the selective O-methylation of diketone, 3-hydroxy-1-(4-methoxybenzyl)-4-propionyl-5,6-dihydro-1H-pyridin-2-one, with dimethyl sulfate and cesium carbonate in dimethylformamide, a one-pot pyrazole formation with subsequent acidic deprotection to provide lactam, 1-cyclopentyl-3-ethyl-1,4,5,6-tetrahydropyrazolo[3,4-c]pyridin-7-one, and finally the utilization of imidate, 1-cyclopentyl-7-ethoxy-3-ethyl-4,5-dihydro-1H-pyrazolo[3,4-c]pyridine for the introduction of the triazole moiety. This process avoided the use of harsh reaction conditions, undesirable reagents and overcame the environmental concerns in the original synthesis.