Kristallstruktur und absolute Konfiguration von (+)-Meloscin-Nb-methobromid

The crystal structure of the N_b-methobromid of the alcaloid meloscin has been determined by three-dimensional X-ray crystallographic methods. The crystals belong to the orthorhombic space group P2₁2₁2₁ with four molecules per unit cell. The cell constants are a = 10.01, b = 17.79, c = 11.43 Å. The absolute configuration has been obtained by the use of anomalous dispersion effects.     

Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher Herkunft

The Absolute Configuration of Iridals and Cycloiridals of Different Origin Natural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C₃₁-triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco-ring-A iridal has the same stereo-chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.     

Über die Synthese der Pilocarpus-Alkaloide Isopilosin und Pilocarpin,sowie die absolute Konfiguration des (+)-Isopilosins

A novel synthesis for rac-pilosinine ( 6 rac) and transformation of (+)-pilosinine ( 6 ) into the pilocarpus alkaloids (+)-isopilosine ( 9 ) and (+)-pilocarpine ( 18 ) are described. By correlation via 5 with 18 the absolute configuration of (+)-isopilosine ( 9 ) is established.     

Die Kristallstruktur und absolute Konfiguration von Mikrolin

The Crystal Structure and Absolute Configuration of Mikrolin. The crystal structure and absolute configuration of mikrolin has been determined by X-ray diffraction. Crystals of mikrolin belong to space group P2₁2₁2₁ with a = 17.867, b = 7.947, c = 9.824 Å, Z = 4. The structure was solved by multi-solution method, and refined to R = 0.060. The anomalous scattering of CuKα-radiation by chlorine was used to determine the absolute configuration of the molecule.     

Über die absolute Konfiguration der Visnagane

(+)-cis-Khellactone methyl ether ( 4 ) and (?)-trans-khellactone methyl ether ( 6 ) had earlier been assigned the absolute configurations 3′-S; 4′-S and 3′-S; 4′-R, respectively, on the basis of the FREUDENBERG , rule. Both compounds together with their defunctionalised derivatives (?)- 7 and (+)- 8 (=(+)-lomatin), obtained from a mixture of (+)-visnadin ( 1 ) and (+)-samidin ( 2 ), were investigated by the HOREAU method. A conformational analytical study showed that the optical yield should rise in the order 4 < 6 < 7 , 8. This order was found and the α-phenylbutyric acid liberated was always dextrorotatory. The centre 3′ of the khellactones and their derivatives must be R-chiral and not S. Treatment of (?)- 6 with pyridinium perbromide gave (?)-trans-3-bromokhellactone methyl ether ( 11 ) as orthorhombic crystals. The X-ray crystal structure determination was made using the anomalous scattering of the Mo-K α radiation by Br. The result, — centre 3′ R-chiral (fig. g) — showed that the HOREAU method was correct.     

Über die absolute Konfiguration der Cantharsäure und des Palasonins

The absolute configurations of (+)-cantharic acid, a chiral derivative of the achiral insect defensive substance cantharidin ( 1 ), and of palasonin, a lower homologue of 1 occurring in the plant Butea frondosa, were shown to be represented by formulas 2 and 3 , respectively (scheme 1). These results were obtained by application of the Horeau method (table 1) on the (+)-cantharic acid derivatives (+)- 5 , (?)- 7 , and (?) 11 (scheme 2), and the palasonin derivatives (+)- 29 and (+)- 30 (scheme 4), as well as by comparison of the chiroptical properties (tables 2 and 3) of a number of derivatives, prepared from either cantharic acid or palasonin. – Attempts to incorporate various radioactively labelled precursors into palasonin ( 3 ), using young and adult plants, have been so far unsuccessful.     

Die absolute Konfiguration von Carquejol und verwandten o-Menthan-Derivaten

The structure of carquejol is amended to that of cis-3-hydroxy-o-mentha-1(7),4,8-triene; the chirality has been confirmed as 2 R, 3 S by correlation with the (?)-cis-o-menthane obtained from carquejol and that from (+)-verbenene of known absolute configuration. The two double bonds of the dihydrocarquejol system ( 15 and 16 ) constitute a helical system, that especially in the case of the acetate ( 16 ) fixes the isopropenyl group in such a way that a very high Δ? value in the CD. curve is observed. The conformational significance of this phenomenon is discussed.     

Totalsynthese und absolute Konfiguration von natürlichem Multifloramin

The diphenol 1 was resolved into its antipodes and their absolute configuration was established. The levorotatory isomer R-(?)- 1 was oxidized to the dienone R-(?)- 6 , which was rearranged to afford natural (?)-multifloramine (R-(?)- 7 ), thus establishing that the latter has the R-configuration. By the same reaction sequences, the enantiomeric diphenol S-(+)- 1 was transformed to provide (+)-multifloramine (S-(+)- 7 ) of the S-configuration.     

Konstitution und elektrochemisches Verhalten der Proteine

Ohne Zusammenfassung Hauptvortrag gehalten am 10. VI. 1930 in der VIII. Hauptversammlung der Kolloidgesellschaft in Frankfurt a. M.     

Trennung und absolute Konfiguration der C(8)-epimeren (all-E)-Neochrome (Trollichrome) und -Dinochrome

Separation and Absolute Configuration of the C(8)-Epimeric (app-E)-Neochromes (Trollichromes) and -Dinochromes The C(8′)-epimers of (all-E)-neochrome were separated by HPLC and carefully characterized. The faster eluted isomer, m.p. 197.8–198.3°, is shown to have structure 3 ((3S,5R,6R,3′S,5′R,8′R)-5′,8′-epoxy-6,7-dodehydro-5,6,5′,8′-tetrahydro-β,β-carotene-3,5,3′-triol). To the other isomer, m.p. 195-195.5°, we assign structure 6 , ((3S,5R,6R,3′S,5′R,8′R)-5′,8′-epoxy-6,7-didehydro-5,6,5′,8′-tetrahydro-β,β-carotene-3,5,3′-triol). The already known epimeric dinochromes (= 3-O-acetylneochromes) can now be formulated as 4 and 5 , (‘epimer 1’ and its trimethylsilyl ether) and 7 and 8 , (‘epimer 2’ and its trimethylsilyl ether), respectively.     

Anreicherung der Enantiomeren,Circulardichroismus und absolute Konfiguration vonN,N,N′,N′-Tetramethyldithiooxamid

(+)- and (?)-1 (N,N,N′,N′-Tetramethyldithiooxamide) were enriched by semipreparative liquid chromatography on triacetylcellulose. According to¹HNMR in the presence of an optically active auxiliary, the sample of (+)₃₆₅-1 had an enantiomeric purity of 0,50±0,01, thus permitting to calculate the CD spectrum for the pure enantiomer. The CD and UV spectra are discussed in terms of qualitative MO theory. Thereby, the absolute configuration of (+)₃₆₅-1 is determined to be (R).