
TY  - JOUR
A1  - Bourke, David G. 
A1  - Collins, David J. 
T1  - The Conversion of Steroidal Ring B Lactones into Ortho Esters: Preparation of 7,7-Dimethoxy-6-oxaestra-1,3,5(10)-triene Derivatives
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1998
VL  - 51
IS  - 11
SP  - 1003
EP  - 1018
KW  - 
UR  - https://doi.org/10.1071/C97179 
N2  - 17&#946;-t-Butyldimethylsilyloxy-3-methoxy-6-oxaestra-1,3,5(10)-trien-7-one (1), prepared in three steps from 17b-hydroxy-3-methoxy-6-oxaestra-1,3,5(10),8-tetraen-7-one (5a), was converted via the corresponding phenolic acid into 1&#946;-t-butyldimethylsilyloxy-5&#946;-(2&#8242;-t-butyldimethylsilyloxy-4&#8242;-methoxyphenyl)-N,7a&#946;-dimethyl-N-phenyl-2,3,3a&#945;,4,5,6,7,7a-octahydro-1H-indene-4&#945;-carboxamide (17c). Subjection of (17c) to a reaction sequence with methyl trifluoromethanesulfonate, sodium methoxide/methanol, and then dry methanol/acetic acid gave a low yield (12%) of the ortho ester 3,7,7,17&#946;-tetramethoxy- 6-oxaestra-1,3,5(10)-triene (2b), together with 5&#946;-(2&#8242;-hydroxy-4&#8242;-methoxyphenyl)-1&#946;-methoxy-N,7a&#946;-dimethyl-N-phenyl-2,3,3a&#945;,4,5,6,7,7a-octahydro-1H-indene-4&#945;-carboxamide (17e) (29%), 8% of (17a), the 1&#946;-hydroxy analogue of (17e) and 3% of methyl 5-(2&#8242;-hydroxy-4&#8242;-methoxyphenyl)-1&#946;-methoxy-7a&#946;-methyl-2,3,3a&#945;,4,5,6,7,7a-octahydro-1H-indene-4&#945;-carboxylate (11c). The outcome of this reaction sequence was complex, and very sensitive to minor changes in conditions. Several related transformations are described, and possible mechanistic pathways are discussed. 
ER  -

