Practical Synthesis of Fluorous Oxazolidinone Chiral Auxiliaries from α-Amino Acids
摘要:
A series of new fluorous-supported oxazolidinone chiral auxiliaries has been prepared using a versatile and general five-step pathway, starting from readily available chiral a-amino acids. The key feature of this synthesis is the efficient generation of a suitably active perfluoroalkyllithium species. By use of this protocol, the auxiliaries can be obtained in high enantiomeric purity and on multigram scales from L-phenylalanine and L-valine with overall yields as high as 55%. The new methodology also incorporates fluorous solid-phase extraction on the large scale, allowing bulk quantities (up to 25 g) of fluorous compounds to be purified from the crude reaction mixture.
An expeditious synthesis of (2R,3S)-3-amino-4-cyclohexyl-2-hydroxybutyric acid (2) and (2S,3R)-3-amino-2-hydroxy-4-phenylbutyric acid (4), the key components of the renin inhibitor (1) and bestatin (3), respectively, have been accomplished by featuring highly diastereoselective formation of cyanohydrin acetates from α-alkoxycarbonylamino aldehydes under phase-transfer conditions.
The title compounds, which are synthetic intermediates of renin inhibitors, could be prepared from (S)-leucine and (S)-phenylalanine, respectively, by employing highly stereoselective aldol reactions of O-methyl-O-trimethylsilyl ketene acetal with an (S)-α-amino aldehyde in the presence of titanium(IV) chloride as a key step. Maximum diastereoselectivity of the aldol reaction was found to be more than 95 : 5.
Fluorous Oxazolidinone Chiral Auxiliary Compounds and Methods of Manufacture
申请人:Hultin Philip Gregory
公开号:US20090018343A1
公开(公告)日:2009-01-15
The present invention relates generally to perfluoroalkyl chiral auxiliary compounds and methods of manufacture. These compounds have the functionality to effectively support the synthesis of chiral compounds in single reactions, high-throughput parallel reactions, or combinatorial reactions The invention relates to two oxazolidinone chiral auxiliaries (1) and (2): wherein R
f
is a perfluoroalkyl group having the general formula (CH
2
)
x
—C
y
F
2y+1
where x=1-5 and y=4-10 and wherein B is an unfunctionalized aryl, alkyl or arylalkyl group in a preferred embodiment, x=2 and y=6 and B is derived from unfunctionalized amino acids The amino acids may be from either the D- or L-series, and are preferably enantiomerically pure or in very high enantiomeric excess in either configuration.