Minoru Ohno

Solvent effect in a partial asymmetric synthesis—I

Abstract The cis/trans ratio as well as trans -(−)-( R : R )/(+)-( S : S ) ratio of cyclopropane products in the NaH-catalyzed Michael type condensations of (−)-menthyl chloropropionate with methyl methacrylate, conducted in media of varying dielectric constant, unequivocally showed the dependence of stereoselectivity of the reaction on solvent polarity. The stereochemical results were explicable in terms of electrostatic stabilization and non-bonded interactions in the postulated transition state conformations stabilized by orbital overlap in the rate- and therefore, stereochemistry-determining cyclization step. The solvent effect was also correlated fairly well in quantitative terms by the Kirkwood-Onsager theory.

Blätteralkohol (XVI)Blätteralkohol (XVII)

2-Methyl-4, 6-cyclohexadienaldehyde and n-butyraldehyde were treated with sodium in p-xylene to yield the aromatized “leaf alcohol reaction” product, 2-methyl-benzylalcohol, in a better yield than that with the cyclohexadienaldehyde alone. n-Butyric acid isolated from the reaction mixture unequivocally showed the operation of the “crossed Cannizzaro disproportionation” in this reaction, aliphatic aldehyde serving as the hydride donor. 2-Propyl-5-ethyl-4, 6-cyclohexadienaldehyde was obtained by the NaOH/H2O-EtOH Michael-Aldol condensation of leaf aldehyde, gave 2-propyl-5-ethyl-benzylalcohol along with caproic acid.On the basis of “leaf alcohol-reaction” mechanism, it was obtained following benzyl-alkohols; 2-methyl-, 2-propyl-, 2-methyl-5-ethyl-, 2-propyl-5-ethyl-benzylalcohol, from leaf alcohol and crotylalcohol.

Blätteralkohol (XIV) Synthese des 2-Propyl-5-äthyl-benzylalkohols

2-Propyl-5-ethyl-benzylalcohol (IX) was synthesized by an unequivocal route from propylbenzene, thereby establishing the previous deduction tentatively assigned to the leaf alcohol reaction product.1) This benzyl alcohol surmises one of a lemon-like flavor characteristic of manufactured black tea and an attempted search for this compound in the essential oil obtained by steamdistillation of manufactured black tea was made, but its existence has not so far been confirmed with a neutral fraction examined.

Studies on the Syntheses of the Pyrethrin Analogues and their Biological Activities: Part II. Relationship between the Stereochemistry and the Biological Activities

The separation of (±) -2,2-dimethyl-3- (3′,4′-methylenedioxyphenyl) -cyclopropane-1-carboxylic acid into the geometrical isomers and the assignment of their configurations were achieved. Of the two isomers, the (±) -trans-acid, which was found more toxic when esterified with (±) -allethrolone, was resolved by means of an optically active α-phenylethylamine salt into (+) - and (-) -enantiomers. (IR:3R) -Configuration was assigned to the (+) -trans-acid and (IS:3S) -configuration to the (-) -trans-acid. The bioassay revealed that the (±) -allethrolone ester with the (+) -trans-acid, which belongs to the same optical series as the natural chrysanthemum acids, was the most toxic against common houseflies, as was the case with other pyrethroids.

Blätteralkohol (IX): Eine einfache Synthese and Konfiguration des Blätteraldehyds

Blatteraldehyd wurde durch die einfachste, ergiebigste Synthese dargestel1t. Demnach wurde es aufgeklart, das die Konfiguration des naturlichen Blatteraldehyds trans-Form ist.

Blätteralkohol (VIII):Über das Vorkommen des trans -Isomeren in der natürlichen Blätteralkohol-fraktiontt

S Blätteralkohol (VIII) : Über das Vorkommen des trans-Isomeren in der natürlichen Blätteralkohol-fraktion Akikazu HATANAKA und Minoru OHNO Bull. Agr. Chem. Soc. Japan, 24, 61 (1960) Es wurde aufgeklärt, dass die in Tee-blättern weit verbreitet vorkommende natürliche Blätteralkohol-fraction aus einem Gemisch der cis, trans-Isomere besteht, wobei bisher das cis-Isomere stark überwiegt. Darstellung von n-Hexin-1-olen und n-Hexen-1-olen Akikazu HATANAKA, Masayuki HAMADA und Minoru OHNO Bull. Agr. Chem. Soc. Japan, 24, 115 (1960) Die theoretisch möglichen sieben geometrischen Isomere von n-Hexen-1-olen und vier Stellungsisomere von n-Hexin-1-olen wurden in geometrisch reinen Formen erhalten. Die einigen davon waren zwar schon bekannt, aber in geometrischen Beziehungen sehen sie noch nicht ganz rein aus. Vier Isomere von n-Hexin-1-olen, die Ausgangsmaterialien zur Darstellung der transoder cis-Hexen-1-olen wurden in jeden Fällen von Acetylen aus über Acetylennatrium in flüssigem Ammmoniak synthesitiert. Besonders war diese Darstellungsmethode von 4und 5-Hexin-1-ol in der Ausbeute bedeutend überlegen als die bisherige. 2-, 3und 4-trans-Hexen-1-ol und 5-Hexen-l-ol wurden durch die Halbhydrierung der entsprechenden n-Hexin-1-olen mit Natrium in flüssigem Ammoniak gewonnen, während 2-, 3und 4-cis-Hexen-l-ol durch die Halbhydrierung in Gegenwart von Palladium-Bariumsulfat bei —15° geliefert wurden. Diese Alkohole wurden über 3, 5-Dinitrobenzoat gereinigt. Die Infrarotspektren von diesen Verbindungen ergaben die verschiedenen interessanten Probleme. The Absolute Configuration of trans-Caronic and cisand trans-Umbelluraric Acids H. M. WALBORSKY, Toshio SUGITA, Minoru OHNO and Yuzo INOUYE J. Amer. Chem. Soc., 82, 5255 (1961) Partial asymmetric syntheses of ( —)-, and (±)-trans-caronic acids were achieved by addition of ethyl diazoacetate to (—)-menthyl senecioate and by that of dimethyldiazomethane to (--)-dimenthyl fumarate respectively in 15.9% and 6.3% optical yields. These results provide cogent support for the use of Prelog-Cram model to this asymmetric synthesis. The addition of ethyl diazoacetate to ( —)menthyl a-isopropylacrylate gave (—)-cis-, and (—)-trans-Umbellularic acids. Bas( 255 )