Boron, Trichloride as a Selective Demethylating Agent for Hindered Ethers: a Synthesis of the Phytoalexins α- and Β-Pyrufuran, a Synthesis of Tri-O-methylleprolomin and its Demethylation

1985 ◽  
Vol 38 (5) ◽  
pp. 777 ◽  
Author(s):  
CF Carvalho ◽  
AV Russo ◽  
MV Sargent
Keyword(s):  
Boron Trichloride ◽  
Demethylating Agent ◽  
Methoxy Groups ◽  
Sterically Hindered ◽  
Derivatives Of ◽  
Lichen Metabolite ◽  
Efficient Reagent

Boron trichloride has been found to be an efficient reagent for the selective cleavage of sterically hindered methoxy groups in methoxyarenes . The scope and utility of this reaction are explored with examples drawn from derivatives of benzene, naphthalene, 9,10- dihydrophenanthrene and dibenzofuran. The method is applied to the synthesis of the phytoalexins α-(56) and β- pyrufuran (58) (1,3,4- trimethoxydibenzofuran-2-ol and 1,2,4-trimethoxydibenzofuran-3-ol). A synthesis of tri-O- methylleprolomin (61), a derivative of the unusual lichen metabolite leprolomin (60), is described and its demethylation with boron trichloride is studied.

Bis(ether) derivatives of tetrakis(2-hydroxyphenyl)ethene — Direct synthesis of (E)- and (Z)-bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene via the McMurry olefination reaction

2006 ◽  
Vol 84 (10) ◽  
pp. 1250-1253 ◽  
Author(s):  
Mee-Kyung Chung ◽  
Paul Fancy ◽  
Jeffrey M Stryker
Keyword(s):  
Supramolecular Chemistry ◽  
Direct Synthesis ◽  
Protecting Groups ◽  
Tert Butyl ◽  
Orthogonal Protection ◽  
Protection Strategies ◽  
Titanium Trichloride ◽  
Sterically Hindered ◽  
Derivatives Of

The direct synthesis of sterically hindered, partially etherified derivatives of tetrakis(2-hydroxyphenyl)ethene is reported by using the McMurry reductive olefination reaction on a range of differentially substituted 2,2′-dialkoxy benzophenone substrates. Three orthogonal protection strategies are demonstrated, incorporating β-silylethyl, 3-butenyl, and tert-butyl protecting groups, respectively, into the starting benzophenones. The latter proved most efficient, with both the McMurry coupling and deprotection steps occurring concomitantly under the McMurry conditions to directly yield the desired bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene as a 1:1 mixture of E- and Z-diastereoisomers.Key words: preorganized polyaryloxide ligands, McMurry olefination, titanium trichloride, supramolecular chemistry, tetrakis(2-hydroxyphenyl)ethene, 2,2′-disubstituted benzophenone.

scholarly journals Synthesis and Comparative Evaluation of Polymethoxy Substituted 1,4-Naphthoquinones and their Acetyl-O-glucosides as Cytotoxic Agents

2017 ◽  
Vol 12 (7) ◽  
pp. 1934578X1701200 ◽  
Author(s):  
Yuri E. Sabutski ◽  
Marina N. Semenova ◽  
Ekaterina A. Yurchenko ◽  
Nikita S. Polonik ◽  
Vladimir A. Denisenko ◽  
...  
Keyword(s):  
Comparative Evaluation ◽  
Ehrlich Ascites Carcinoma ◽  
Carcinoma Cells ◽  
Cytotoxic Agents ◽  
Cytotoxic Effects ◽  
Micromolar Concentration ◽  
Sea Urchin Embryo ◽  
Ehrlich Ascites ◽  
Methoxy Groups ◽  
Derivatives Of

Twenty five hydroxy-, chloro- and methoxy derivatives of natural and synthetic naphthazarins and their acetylated O-glycosides were synthesized. Targeted compounds were screened as cytotoxic agents on mouse Ehrlich ascites carcinoma cells using MTT test. Chloro- and methoxy-substituted naphthoquinones as well as naphthoquinone O-acetylglucosides were the most potent with IC50 in low micromolar concentration range. Glucosidation of hydroxynaphthoquinones was shown to enhance cytotoxicity, whereas methoxylation yielded both more active and less active derivatives depending on the number and position of methoxy groups. Evaluation using a phenotypic sea urchin embryo assay suggested that naphthazarins exerted their cytotoxic effects through tubulin-unrelated mechanism.

Introduction of 9-fluorenylmethyloxycarbonyl, trichloroethoxycarbonyl, and benzyloxycarbonyl amine protecting groups into O-unprotected hydroxyamino acids using succinimidyl carbonates

1982 ◽  
Vol 60 (8) ◽  
pp. 976-980 ◽  
Author(s):  
Alenka Paquet
Keyword(s):  
Benzyl Ester ◽  
Protecting Groups ◽  
Efficient Conversion ◽  
Hydroxyamino Acids ◽  
High Yields ◽  
Derivatives Of ◽  
Acid Esters ◽  
Efficient Reagent

9-Fluorenylmethyl succinimidyl, pentachlorophenyl, and benzotriazole-1-yl carbonates were prepared and their reactivity with L-serine and L-serine benzyl ester was compared. The most efficient reagent, 9-fluorenylmethyl succinimidyl carbonate, was used for the preparation of 9-fluorenylmethyloxycarbonyl derivatives of other hydroxyamino acids and hydroxyamino acid esters in high yields. The use of trichloroethyl and benzyl succinimidyl carbonates for an efficient conversion of hydroxyamino acids and their esters into the corresponding N-trichloroethoxycarbonyl and benzyloxycarbonyl derivatives is described.

Peroxides of Sterically Hindered Derivatives of Schlenk Hydrocarbon Diradical

1997 ◽  
Vol 62 (19) ◽  
pp. 6524-6528 ◽  
Author(s):  
Andrzej Rajca ◽  
Suchada Rajca ◽  
Shailesh R. Desai ◽  
Victor W. Day
Keyword(s):  
Sterically Hindered ◽  
Derivatives Of
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