ASTLES, PETER C.;THOMAS, ERIC J., SYNLETT.,(1989) N, C. 42-45
作者:ASTLES, PETER C.、THOMAS, ERIC J.
DOI:——
日期:——
Syntheses of thunbergols and α- and β-cembra-2,7,11-triene-4,6-diols
作者:Peter C. Astles、Eric J. Thomas
DOI:10.1039/a606551a
日期:——
Alkylation of the racemic sulfone 25, available from the
epoxide 8, using the iodide 24 followed by reduction gives the
protected hydroxy acetal 27. Selective deprotection gives the
alcohol 28. This is converted into the bromide 29 which is used
to alkylate the keto phosphonate 33. Hydrolysis of the alkylated
keto phosphonate 30 gives the aldehyde 31 which is cyclised under
mild conditions (63%) and the product treated with
methylmagnesium iodide, to give the racemic thunbergols 3 and 4,
in a ratio of 3â¶4 = 10â¶90. The
laevorotatory sulfone 25 has been prepared by regioselective
ring-opening of the epoxide 38 followed by hydrogenation,
selective protection and functional group modification. After
alkylation of this sulfone using the iodide 24 and conversion
into the aldehyde 46, an asymmetric aldol condensation gives the
hydroxy amide 47 which is converted directly into the hydroxy
keto phosphonate 49 by reaction with an excess of lithiated
dimethyl methylphosphonate. After protection of the hydroxy
group, selective hydrolysis of the acetal gives the aldehyde 51
which is cyclised as before to give the naturally occurring
cembratrienediols 1 and 2 after reaction with methylmagnesium
iodide and deprotection.