A synthesis of the phenolic lipid, 3-[(Z)-pentadec-8-enyl] catechol, (15:1)-urushiol.
A synthesis of (15:1)-urushiol, urushiol monoene, 3-[(Z)-pentadec-8-enyl] catechol, 1,2-dihydroxy-3-[(Z)-pentadec-8-enyl] benzene, one of the toxic principles of Rhus toxicodendron and of Rhus vernicifera is described. 6-Chlorohexan-1-ol protected at the OH group with ethyl vinyl ether reacted with 2,3-dimethoxybenzaldehyde in the presence of lithium to give, after removal of the protective group with methanolic 4-toluenesulphonic acid, 1-(2,3-dimethoxyphenyl) heptane-1,7-diol. Catalytic hydrogenolysis in ethanol with palladium-carbon selectively afforded 7-(2,3-dimethoxyphenyl)heptane-1-ol accompanied by a small proportion of the 7-(3-methoxyphenyl)heptane-1-diol, formed by demethoxylation. Reaction of the dimethoxy compound with boron tribromide resulted in both bromination and demethylation to give 7-(2,3-dihydroxyphenyl) heptylbromide. This bromide in tetrahydrofuran (THF) containing hexamethylphosphoric triamide reacted with excess lithium oct-1-yne to give 3-(pentadec-8-enyl)catechol which, by catalytic hydrogenation in ethyl acetate containing quinoline, selectively formed the required cis product, 3-[(Z)-pentadec-8-enyl]catechol which was identical chromatographically and spectroscopically with urushiol monoene separated from the natural product.
Tyman
John H P
JH
Department of Chemistry, Brunel University, Middlesex UB8 3PH, Uxbridge, UK. jhptyman@hotmail.com
Schofield
Brian G
BG
Khor
Choong H
CH
D002396:Catechols / Q000138:chemical synthesis*; D003885:Dermotoxins / Q000138:chemical synthesis* / Q000302:isolation & purification; D008055:Lipids / Q000138:chemical synthesis*; D010936:Plant Extracts / Q000138:chemical synthesis / Q000302:isolation & purification; D029045:Rhus / Q000737:chemistry; D012251:Toxicodendron / Q000737:chemistry
D002396:Catechols; D003885:Dermotoxins; D008055:Lipids; D010936:Plant Extracts