
TY  - JOUR
A1  - Collins, J 
A1  - Cooper, PS 
A1  - Gall, RE 
A1  - Georges, A 
T1  - Bromination of 5a-lanost-8-en-3-one and 5a-lanost-8-ene-3,7,ll-trione
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1982
VL  - 35
IS  - 4
SP  - 857
EP  - 861
KW  - 
UR  - https://doi.org/10.1071/CH9820857 
N2  - Monobromination of 5&#945;-lanost-8-en-3-one (la) under kinetic conditions gave exclusively the 2&#946;- bromo ketone (3a) whilst under equilibrium conditions the product contained 85% of the 2&#945;-bromo ketone (2a). Monobromination of 5a-lanost-8-ene-3,7,11-trione (1b) under kinetic conditions gave the 2a-bromo ketone (2b); 33% of the 2&#946;-bromo ketone (3b) was formed under equilibrium conditions. The configuration assigned to the bromo ketones (2b) and (3b) has been confirmed by reduction with sodium borohydride and treatment of the derived bromohydrins (4b) and (6b) with base to give the 2&#946;,3&#946;-epoxide (5b) and the 3-ketone (1b) respectively. Cleavage of the 2&#946;,3&#946;(-epoxide (5a) with acetic acid gave 2&#945;-acetoxy-5&#945;-lanost-8-en-3&#946;-ol (7) as the major product and 3&#945;-acetoxy-5&#945;-lanost- 8-en-2&#946;-ol (a), in a boat like conformation, as the minor product. 
ER  -

