Synthese und Chiralität von (5R, 6R)-5,6-Dihydro-β, ψ-carotin-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotin-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β, ψ-carotin und (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-carotin

Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-carotene Wittig-condensation of optically active azafrinal ( 1 ) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol ( 2 ) and (+)-(R)-α-ionol ( 5 ) leads to the crystalline and optically active carotenoid diols 4 and 7 , respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9 , respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].     

Synthese und Chiralität von (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,β-carotin und (5R, 6R)-5,6-Dihydro-β,β-carotin-5,6-diol,einem Carotinoid mit ungewöhnlichen Eigenschaften

Synthesis and Chirality of (5S,6R)-5,6-Epoxy-5,6-dihydro-β,β-carotene and (5R,6R)-5,6-Dihydro-β,β-carotene-5,6-diol, a Compound with Unexpected Solubility Characteristics Wittig-condensation of azafrinal ( 1e ) with the phosphorane derived from 7 leads to a (1:3)-mixture of (E)-9′- and (Z)-9′-β,β-carotene-diol 3 , from which pure and optically active 3 ((5R,6R)-5,6-dihydro-β,β-carotene-5,6-diol) has been isolated as bright violet leaflets, m.p. 168°. Due to the trans-configuration of the diol moiety and to severe steric hindrance, hydrogen bonding is reduced to such an extent, that 3 behaves much more as a hydrocarbon than as a diol. There is good evidence that the so-called ‘β-oxycarotin’ obtained by Kuhn & Brockmann [15] by chromic acid oxidation of β, β-carotene is the corresponding racemic cis-diol. 3 has been converted into (5S, 6R)-5,6-epoxy-5.6-dihydro-β,β-carotene ( 4 ), m.p. 156°. This transformation establishes for the first time the chirality of a caroteneepoxide (without other O-functions). Full spectral and chiroptical data including a complete assignement of ¹³C-chemical shifts for azafrin methyl ester and 3 are presented.     

Synthese von (−)-(5R,6S)-5,6-Epoxy-5,6-dihydro-β-ionon

Synthesis of (?)-(5R,6S)-5,6-epoxy-5,6-dihydro-β-ionone Optically active 5,6-epoxy-5,6-dihydro-β-ionones have been prepared for the first time and their absolute configurations were determined by correlation with (?)-(S)-α-ionone. Acid catalyzed hydrolysis of the epoxide proceeds with retention of the configuration at C(6) and with inversion at C(5).     

Polymerization of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose and 1,2-O-isopropylidene-α-D-glucofuranose

A new method for preparing D -glucose polymers is described. Isopropylidene derivatives of D -glucofuranose, particularly the 1,2-mono-O-derivative, are treated with Lewis acids, such as boron trifluoride, to eliminate acetone and produce a highly branched polymer with a molecular weight of 12,700. Approximately one isopropylidene unit remains, possibly on the potential reducing end of the glucan. Up to 95% of the polymer units are D-glucopyranoside units indicating that ring expansion occurs during the condensation.     

Synthesis of 1,2:5,6-Di-O-isopropylidene-3-O-[3-(uracil-1-yl)propionoyl]-α-D-glucofuranose and 1,2-Mono-O-isopropylidene-6-O-[3-(uracil-1-yl)propionoyl]-α-D-glucofuranose

1,2:5,6-Di-O-isopropylidene-3-O-[3-(uracil-1-yl)propionoyl]-α-D-glucofuranose and 1,2-mono-O-isopropylidene-6-O-[3-(uracil-1-yl)propionoyl]-α-D-glucofuranose were synthesized.