34487-52-0Relevant articles and documents
Regioselective Ether Cleavages of Rotenoids: Spiro-ether Formation and Stereoselective Isotopic Labelling of (E)- or (Z)-Phenyl Methyl Groups in (6aS, 12aS)-Rot-2'-enonic Acid
Carson, David,Crombie, Leslie,Kilbee, Geoffrey W.,Moffatt, Frank,Whiting, Donald A.
, p. 779 - 788 (2007/10/02)
Treated with boron tribromide (-)-(6aS,12aS,5'R)-rotenone is converted first into a primary allylic bromide by ring-E cleavage, then into the 2-de-O-methyl and finally the 2,3-dide-O-methyl derivatives.With (6aS,12aS,5'R)-6',7'-dihydrorotenone and (6aS,12aS)-isorotenone, ring-E cleavage does not take place.The main reaction is 2-, followed by 2,3-demethylation: this supports a stereospecific pericyclic mechanism for the rotenone ring-E cleavage.Treatment of the geometrically pure (E)-bromide with cyanoboro-deuteride or -tritide leads to (E)-4'-labelled (6aS,12aS)-rot-2'-enonic acid without reduction of the 12-carbonyl group.By using -rotenone, (E)-rot-2'-enonic acid is accessible.Trimethylsilyl iodide can cleave the 2-methoxy-group of rotenonewithout rupturing ring E, and remethylation with - or -diazomethane represents a convenient method for preparing a general tracer molecule.On treatment with sodium hydride, 3-de-O-methylisorotenone (but not the 2-isomer) rearranges into a spiroether, thus confirming the position of initial de-O-methylation as deduced from 1H and 13C n.m.r. data.Because of this rearrangement, methylenation (NaH-CH2I2) of 2,3-dide-O-methylisorotenone gives mainly the methylenedioxy-spiro-ether, with small yields of methylenedioxy-rotenoid.Deuteriogenolysis of (-)-rotenone over palladium catalyst in (2H5)pyridine gives (E)-rot-2'-enonic acid, but experiments using rotenone indicate stereoselectivity rather than stereospecificity, ca. 12percent of (Z)--accompanying the major (E)-product.A similar specimen of rotenonic acid has been prepared.A hydrogenolysis route from amorphigenin, via rotenone, to (Z)-rot-2'-enonic acid is described.
