Γ-Lakton-cis-anellierung an Δ2- und Δ3- Cholesten

γ-Lactone-cis-annulation to Δ²- and Δ³- Cholestene. From Δ²- and Δ³- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The ¹³C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported.     

Über die Carotinoide Flavoxanthin und Chrysanthemaxanthin: 1H-NMR.-, 13C-NMR.- und Massen-Spektren und absolute Konfiguration. (Kritische Überprüfung veröffentlichter chemischer und physikalischer Daten)

On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: ¹H-NMR., ¹³C-NMR. and Mass Spectra, Absolute Configuration, Survey of Published Data Very pure flavoxanthin ( 1 ) and chrysanthemaxanthin ( 2 ) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa. Chemical degradation of 1 and 2 to (?)-loliolide ( 5 ) coupled with NMR. evidence (ASIS, spin-decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2 . Thus (+)-flavoxanthin is (3S,5R,8R, 3′R,6′R)-5, 8-epoxy-5, 8-dihydro-β, ε-carotene-3, 3′-diol and (+)-chrysanthemaxanthin its C(8)-epimer.     

Calcium–Rhodium–Hydride –- Synthese und Struktur

Calcium Rhodium Hydrides –- Synthesis and Structure The two ternary hydrides Ca₈Rh₅H₂₃ and Ca₈Rh₆H₂₄ can be synthesised by reacting calcium hydride with rhodium in a hydrogen atmosphere. X-ray investigations on powder samples and elastic neutron diffraction experiments on the deuterated compounds led to the complete structures. Both hydrides crystallise in cubic structure types representing a transition from the K₂PtCl₆ type to the perovskit type structure. The rhodium deuterium bond lengths and the atomic volume of deuterium were discussed.     

Kristall- und Molekülstruktr von N,N′, N″- Trimethyl-N″- methylcarbamoylguanidiniumchlorid

N, N′, N″- Trimethyl-N″-Methyl-Carbamoylguanidinium Chloride The title compound is formed in small amounts by the chlorination of N, N′-dimethylurea with phosgene as a consecutive product, which crystallizes in the triclinic space group P1 with two formula units per cell. The cross-linkage of these two molecules with relative short N? H…?Cl…?H? N- bridges forming large, 16- membered ring systems is remarkable. The structure was refined to an R-value of 0.03.