ISSN:0018-019X    

DOI:10.1002/hlca.19780610602

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Absolute Configuration of α‐Doradexanthin and of Fritschiellaxanthin, a New Carotenoid fromFritschiella tuberosaIYENG.Fritschiellaxanthin, a new oxocarotenoid produced by the green algaFritschiella tuberosa, in a nitrogen‐deficient medium is now shown to be (3S, 3′R, 6′R)‐3, 3′‐dihydroxy‐β, ϵ‐caroten‐4‐one (4b). It is not identical with α‐Doradexanthin (5b) previously found in goldfish (Carassius auratus) and to which we assign the (3S, 3′S, 6′R)‐chirality. Consequently, fritschiellaxanthin and α‐Doradexanthin are C(3′)‐epimers of lutein‐4‐on. Furthermore, the so‐called ′lutein′ from goldfish has now been found to be identical with 3′‐epilutein(3). Therefore, fritschiellaxanthin is probably biogenetically derived from lutein(2), whereas α‐Doradexanthin is formed from 3′‐epilutein(3)with 3,O‐didehydrolutein (=(3R, 6′R)‐3‐hydroxy‐β, ϵ‐caroten‐3′‐one10)as a precursor. For comparison, o

ISSN:0018-019X    

DOI:10.1002/hlca.19780610603

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Edulon A, a Derivative of 2H‐1‐Oxapyrene fromPlectranthus edulis (LabiataeFrom the coloured leaf‐glands of the above mentioned East‐african labiate we have isolated Edulon A, A new, deeply coloured diterpenoid. Based mainly on spectroscopic arguments, we propose its structure to be (5aR, 1′ ζ)‐10‐(2′‐acetoxy‐1′‐methylethyl)‐6, 7, 9‐trihydroxy‐3, 5a‐dimethyl‐4, 5, 5a, 8‐tetrahydro‐2H,‐l‐oxapyrene‐2, 8‐dione(1a). The compound may be regarded as a 4, 5‐seco‐abietane derivative that has formed new bonds (between C(18 or 19)COOH and C(12)OH), and between C(3) and C

ISSN:0018-019X    

DOI:10.1002/hlca.19780610604

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Partial Synthesis of Tetrahydroverrucarin JTetrahydroverrucarin J(18), a macrocyclic triester, has been synthesized from the sesquiterpene alcohol verrucarol(3).

ISSN:0018-019X    

DOI:10.1002/hlca.19780610605

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

The preparation, crystalline structure, properties and behaviour of the hafnium bis (monohydrogen phosphate) monohydrate as a cationic exchanger have been studied. The crystalline product has been characterized by elemental analysis, X‐ray Powder patterns, thermal analysis, photoelectron spectrometry and infra red spectroscopy. A layered structure in which the hafnium and phosphorus atoms are disposed in such a way as to form zeolitic‐type cavities is suggested. The reversibility of the exchange with respect to sodium ions is discussed and can be related to the water content of the exchan

ISSN:0018-019X    

DOI:10.1002/hlca.19780610606

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe molluscicidal principle ofCornus floridaL. (Cornaceae) has been isolated from the methanolic bark extract by droplet counter‐current chromatography (DCC). The structure of the active compounds has been determined as sarsapogenin‐O‐β‐D‐xylopyranosyl‐(1 → 2)‐β‐D‐galactopyranoside(2)and sarsapogenin‐O‐β‐D‐glucopyranosyl‐

ISSN:0018-019X    

DOI:10.1002/hlca.19780610607

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Radical‐induced Intramolecular 1,4‐Transfer of a Formyl GroupA further example of a radical‐induced intramolecular shift of a functional group in steroids is described. In analogy to the sequence leading to the 1, 4‐transfer of cyano groups [3], 11 β‐nitrite photolysis was used to generate the appropriate C (18) radical in the 20‐hydroxy‐11 β‐nitrosyloxy‐pregnene‐21‐al6. Intramolecular addition of the radical center to the double‐bond of the specially adjacent aldehyde function, followed by fragmentation of the intermediate cyclic alkoxy radical and subsequent oxidation lead directly to the rearra

ISSN:0018-019X    

DOI:10.1002/hlca.19780610608

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractMikrolin(8)and dechloromikrolin(9)have been shown to exist as tautomeric mixtures in solution. The structures of mono‐O‐trifluoroacetyl Mikrolin(10)and di‐O‐acetyl Mikrolin(11)have been elucidated. The products15to23from reduction of the metabolites89with Pd/C and Zn in aqueous acetic acid have been identified. The13C‐NMR. spectra of Mikrolin(8)and dechloromikrolin(9)and their derivatives have been completely assigned Based on the results of incorporation experiments with sodium [1‐13C]‐, [2‐13C]‐ and [1, 2‐13C]‐acetate, a biosynthetic pathway is pro

ISSN:0018-019X    

DOI:10.1002/hlca.19780610609

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Extraction of alkali and alkaline earth metal picrates from water into methylene chloride. Quantitative interpretationThe ligandsN, N, N′, N′‐tetraphenyl‐3, 6‐dioxaoctanediamide(1), (−)‐(R, R)‐N, N′di [(ll ‐ ethoxycarbonyl) undecyl] ‐N, N′, 4, 5‐tetramethyl‐3, 6‐dioxaoctanediamide(2), andN, N′‐diheptyl‐N, N′, 5,5‐tetramethyl‐3,7‐dioxanonanediamide(3), reported earlier as components for liquid membrane electodes with selectivity for Ba2+(1), Ca2+(2)and Li+(3), were used to study models for the extraction of alkali and alkaline earth metal picrates from water into methylene chloride. The composition of the extracted complexes of alkaline earth cations with1and2proved to be mono‐ and diassociated with the picrate anion. The extraction selectivity observed for1, 2, and3towards different cations paralleled the potentiometric selectivity factors obtained for liquid membrane el

ISSN:0018-019X    

DOI:10.1002/hlca.19780610610

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe π‐ionization energies of the di‐t‐butylpolyacetylenes with two, three, four and five conjugated triple bonds have been determined by He (Iα) photoelectron spectroscopy. The assignment of the bands to theΠ‐states of the corresponding radical cations follows from simple correlations in agreement with previous experience. The influence of thet‐butyl groups on the ionization energies is rationalized in terms of traditional, qualitative arguments assuming an inductive and/or hyperconjugative mechanism. However, a more careful analysis shows that the ‘The ‐higher‐the‐ionization‐energy‐the‐higher‐the‐alkyl‐induce

ISSN:0018-019X    

DOI:10.1002/hlca.19780610611

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY