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].     

Synthesis of 3β-Hydroxy[21-14C]-5β-pregn-8(14)-en-20-one from Chenodeoxycholic Acid

3β-Hydroxy[21-¹⁴C]5β-pregn-8(14)-en-20-one ( 17 ) was prepared from chenodeoxycholic acid ( 1a ). The synthetic sequence involved: (i) degradation of the bile-acid side chain to an etianic acid; (ii) formation of the 8(14)-double bond; (iii) inversion of the configuration at C(3); (iv) construction of the acetyl side chain at C(17) with the required isotopic label at C(21). Structures of all described products were confirmed by chemical and spectroscopic (IR, ¹H-NMR, ¹³C-NMR, MS) methods.     

Steroid Total Synthesis,Part II; (−)-17β-Hydroxy-des-A-androst-9-en-5-one

Based on the results obtained in the racemic series (part I), (—)-17β-hydroxy-des-A-androst-9-en-5-one has been synthesized, starting with (S)-(—)-5-heptanolide. The key step, viz. the condensation of (S)-(—)-7-hydroxy-1-nonen-3-one (or its amine adduct) with 2-methyl-cyclopentane-1, 3-dione involves an asymmetric induction. Model experiments with (R)-(+)-5-decanolide leading to the enantiomeric homolog of the BCD-tricyclic compound are also described.     

The crystal structure of 5-amino-6-chloro-4-nitro-2-(β-D-ribofuranosyl)-2H-pyridazin-3-one

The nucleoside, 5-amino-6-chloro-4-nitro-2-β-D-ribofuranosyl-2H-pyridazin-3-one ( 4 ), was synthesized as part of a study to prepare potential chemotherapeutic compounds. An X-ray crystal structure study of the compound was initiated in order to substantiate its formula and to examine its conformation and absolute configuration. The structure was determined using direct methods and refined to an R of 0.020 (R_w = 0.024). The compound has a glycosyl torsion angle of 71.2°. The structure contains three intermolecular hydrogen bonds and one intramolecular hydrogen bond.