The degradation of idiospermolide

An earlier post described the degradation of idiospermolide to 29-norcycloartanol. This post gives the experimental and spectral data for the intermediate degradation products.

Ring opening of idiopsermolide with potassium t-butoxide:

After reacting idiospermolide with potassium t-butoxide in t-butanol the crude diene acid (λmax 265 nm) was methylated with diazomethane to give the diene ester which crystallized from methanol as colourless needles, m.p. 149-150° (Found: C: 79.7%; H: 9.8%. C30H46O3 requires C: 79.7%; H: 9.7%). νmax 1705, 1636, 1602, 1451, 1432, 1235, 1200, 1170, 1113, 985 cm-1; λmax 268, nm, ε 25000; mass spectrum (452, (P,22), 420 (30), 326 (12), 299 (90), 292 (70), 283 (12), 281 (14), 257 (16), 229 (18), 215 (20), 203 (28), 189 (64), 175 (80), 154 (100),149 (60), 147 (70), 145 (46), 135 (62), 133 (80)).

Hydrogenation of the diene ester:

The diene ester was hydrogenated with palladium/charcoal to give the saturated ester which crystallized from methanol as colourless prisms, m.p. 83-5-85° (Found: M.W. 456.360 ± 0.003. C30H48O3 requires M.W. 456.3603). νmax 1730, 1708, 1202 cm-1; mass spectrum 456, (P, 53), 441 (21), 425 (7), 409 (10),328 (21), 299 (66), 251 (17), 175 (28), 121 (45), 107 (52), 95 (75), 81 (52), 55 (100).

Conversion of the hydrogenated ester to 29-norcycloartanol:

The ester was reduced with lithium aluminium hydride and the crude diol tosylated with p-toluenesulphonyl chloride. The crude tosylate was reduced with lithium aluminium hydride to produce 29-cycloartanol which crystallized from methanol as colourless needles, m.p. 127-130° (lit. 128-132° G. Berti, F. Bottari, A. Marsili, I. Morelli and M. Palvani, Tetrahedron Lett., 1967, p125), νmax 3700-3300, 1200, 1120 cm-1; mass spectrum: 414 (P,5), 412 (4), 399 (20), 397 (14), 396 (18), 381 (24), 121 (46), 119 (42), 109 (52), 107 (64), 105 (56), 95 (74), 93 (56), 91 (52), 81 (76), 79 (50), 69 (76), 67 (52), 57 (84), 55 (100).

Conversion of cycloeucalenol to 29-norcycloartanol:

The acetate of cycloeucalenol was ozonlyzed to give demethyloxocycloeucalenyl acetate. This was reduced with sodium borohydride, tosylated with p-toluenesulphonyl chloride and then reduced with lithium aluminium hydride. The product was identical with the 29-norcycloartanol prepared via degradation of idiospermolide: the mixed m.p. was undepressed and the i.r. spectra were identical.