A synthesis of the oleanane skeleton

✍ Scribed by J.A. Barltrop; J.D. Littlehailes; J.D. Rushton; N.A.J. Rogers

• Publisher: Elsevier Science
• Year: 1962
• Tongue: French
• Weight: 146 KB
• Volume: 3
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)70896-3

✦ Synopsis

SCLAREOL (I), the synthesis of which has been described elsewhere,1 has been used as a starting material for the synthesis of hydrocarbons of the oleanane series. Permanganate oxidation2 under controlled conditions gave either the hydroxyketone (II, X = -CH2CaCH3; R =*<E),l m.p. 78'-80°, or the enolether (III), b.p. 130~-134~/0.06 mm. Ozonolysis of the latter, in ethyl acetate at -70' gave a mixture of an aldehyde (II, X = CHO; R =-<z) and the corresponding acid.' Lithium aluminium hydride reduction of this product, without purification gave two products; the glycol (II, X = -CH20H; /OH R =,Me , m.p. ) 132', and the unsaturated alcohol (II, X = -ZH20H; R = CH2). Treatment of either with phosphorus oxybromide in pyridine gave, in good yield, the unsaturated bromide (II, X = -CH2Br; R = CH2), b.p. 145'-150°/o.05 mm; [a];5 t31O.

This bromide, in presence of sodium t-amyloxide, alkylated the racemic octalone (IV).4 The product, obtained as a viscous oil in 68 per cent yield, was the mixture of epimeric ketones (V), the synthesis of which, by a different route, has already been described.5 This mixture had Amax 250 mM,