To test our hypothesis, we chose to synthesize 2 via
MOM-protected estradiol.8d,8h First, 1 was treated with a
solution of MOMCl and DIPEA in THF to produce the
doubly MOM-protected estradiol, 5. When treated with
t-BuLi in THF at -40 C, 5 was lithiated on C-2 exclusively,
directed by the MOM protecting group attached on the
phenolic oxygen. This anion was subsequently methoxylated
on C-2 by treatment with cumyl methyl peroxide.
Hydrolysis of the two MOM protecting groups on 6 with
6 N HCl in THF provided compound 2 in high yield. The
overall yield of the three steps was 70%. Other reported
methods using C-2 lithiated MOM-protected estradiol to
synthesize 28c,8d,8h did not introduce the methoxy group
directly onto the lithiated C-2, but went through a combination
of formylation/Bayer-Villiger oxidation/methylation
or boration/oxidation/methylation (Scheme 2). Clearly, our
method is a shorter and more efficient method than the reported
methods.