摘要:

Six novel coumarins have been isolated from the aerial parts ofEriostemon bruceivar.cinereus.Five had the same tricyclic nucleus [(+)-2-methyl-5-hydroxy-2H-benzo-[1,2b:3,4b′]-dipyran-8-one] and varied only in the C-2 substituent,viz.4-methylpent-3-enyl (protobruceol-1), 4-hydroxy-4-methylpent-2(E)-enyl (protobruceol-II), 4-hydroperoxy-4-methylpent-2(E)-enyl (protobruceol-II hydroperoxide), 3-hydroxy-4-methylpent-4-enyl (protobruceol-III), 3-hydroperoxy-4-methylpent-4-enyl (protobruceol-III hydroperoxide). A sixth coumarin was characterised as the linear annellated isomer of protobruceol-II, (+)-2-methyl-2-(4-hydroxy-4-methylpent-2(E)-enyl)-5-hydroxy-2H-benzo-[1,2b:5,4b′]-dipyran-8-one (protobruceol-IV)

ISSN:1057-5634    

DOI:10.1080/10575639208048892

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The structure of lycorenine, an Amaryllidaceae alkaloid isolated fromNarcissus eugeniae, has been completely assigned by 2D NMR methods.

ISSN:1057-5634    

DOI:10.1080/10575639208048893

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The reaction of methyl (Z)-9,10-epoxy-12-oxoocta-decanoate (2) with ammonium azide, generatedin situfrom sodium azide and ammonium chloride in aqueous ethanol affords methyl 8-(5-hexylfuran-2-yl)octanoate (1b) in 98% yield. Compound1bwas also prepared in >90% yield by reacting compound 2 with the following Lewis acids: aluminium(III) chloride, tin(IV) chloride, zinc(II) chloride under reflux in benzene or dichloromethane; or at ambient temperature with tin(II) bromide or hydrated tin(II) chloride in dichloroethane.

ISSN:1057-5634    

DOI:10.1080/10575639208048894

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Two new prenylated flavanonols (1) and (2) isolated from the roots ofMaackia tenuifoliawere synthesized from resacetophenone (3). Prenylation of 3 with prenyl bromide in the presence of methanolic alkali gave 3-C-prenyl resacetophenone (4a), whereas in the presence of silver oxide catalyst, afforded mainly 5-C-prenyl resacetophenone (4b). Condensation of 4a and 4b with benzaldehyde yielded chalcones (5a and 5b) which were converted into racemic epoxides (7a and 7b) after methoxymethylation and epioxidation. Cyclization of epoxides (7a and 7b) resulted in formation of racemic flavanonols (8a and 8b).

ISSN:1057-5634    

DOI:10.1080/10575639208048895

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Electrospray ionization mass spectrometry is a useful new technique for structure determination of alkaloids in solution. Incredibly clean spectra of quinine, strychnine, solasodine, yohimbine, pentazocine and metazocine show only the protonated molecular ion. Increasing the repeller voltage leads to fragmentation showing structural information similar to EI. Non-basic alkaloids such as colchicine show much weaker M+H+and M+Na+ions.

ISSN:1057-5634    

DOI:10.1080/10575639208048896

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Desmosinol, a novel cycloartane triterpenoid was isolated from the stem ofDesmos cochinchinensisLour. (Annonaceae). Its structure was established by spectroscopic methods.

ISSN:1057-5634    

DOI:10.1080/10575639208048897

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Non-aqueous immiscible bi-phase solvent systems have been used for the specific separation of phenolic lipds in cashew nut-shell liquid (CNSL) fromAnacardium occidentale.

ISSN:1057-5634    

DOI:10.1080/10575639208048898

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In callus and cell suspension cultures ofArtemisia annuaminute amounts of artemisinin were found. In these cultures, a high peroxidase activity was measured, intracellularly and, especially, in the medium.In vitro, artemisinin rapidly decomposed when incubated with a cell homogenate ofA. annuaor with spent culture medium, as well as in a solution of commercially obtained horseradish peroxidase (EC 1.11.1.7). In contrast, the peroxidase activity in the intact plant, containing considerable amounts of artemisinin, was low. We suggest that the high peroxidase activity inA. annuacell cultures contributes to their very low artemisinin contents.

ISSN:1057-5634    

DOI:10.1080/10575639208048899

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Reexamination of the stereoselectivity in the epoxidation of 10-membered exocyclic enone and the structure determination of periplanone A and B based on molecular mechanics calculation are described.

ISSN:1057-5634    

DOI:10.1080/10575639208048900

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Deoxycytidine derivatives dibenzoylated at their base moieties existed as equilibrium mixtures of 3,N- andN,N-dibenzoylated species and underwent unusually facile depurination upon treatment with 80% acetic acid.

ISSN:1057-5634    

DOI:10.1080/10575639208048901

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor