(+)-Sch
725680
Organic Letters, 2012, 14, 4303-4305
Toshifumi Takeuchi et al.
The
retrosynthesis of (+)-Sch725680, begins with disconnecting the ester bond, thus
giving acid chloride 13 and alcohol 10 as the main components. Alcohol 10
comes from an hydroxyl addition on to a carbon-carbon triple bond in alkyne 9.
(Synthetically this is accomplished by just acidic treatment of the
in-situ generated alcohol on the conjugated triple bond). Compound 9
comes from an Aldol-condensation of ketone 8,
which is generated by (a) alkyne lithium addition on aldehyde 6,; (b) methyl lithium attack on
Weinreb amide portion of the molecule and finally,; (c) oxidation of the
alcohol formed to the ketone functionality by using PCC. Compound 6
comes by ring-opening of lactone 5
by N, O-dimethylhydroxylamine hydrochloride and oxidation of the primary
alcohol. The protected alcohol 5 comes from diol 4, which is formed by a cyclization of terminal alcohol on the
chiral auxiliary 3. Compound 3
is generated by a titanium mediated aldol reaction of imide 1 with aldehyde 2.
No comments:
Post a Comment