Allylic hydroxy phosphonates: Versatile chiral building blocks
Allylic hydroxy phosphonates are converted into β and γ substituted amino phosphonates using a series of palladium-catalyzed reactions. The judicious selection of nitrogen nucleophile and palladium catalyst allow for excellent regio- and stereochemical co
De La Cruz, Antonette,He, Anyu,Thanavaro, Anchalee,Yan, Bingli,Spilling, Christopher D.,Rath, Nigam P.
p. 2577 - 2592
(2007/10/03)
The synthesis of 1-hydroxy phosphonates of high enantiomeric excess using sequential asymmetric reactions: Titanium alkoxide-catalyzed P-C bond formation and kinetic resolution
Titanium alkoxide-catalyzed asymmetric phosphonylation of aldehydes yields hydroxy phosphonates in moderate to good enantiomeric excess (e.e.s ~70%). The hydroxy phosphonates were acetylated and the acetates were subjected to enzyme-catalyzed kinetic resolution. The non-racemic acetates 2 (predominantly (R)-enantiomer) were hydrolyzed with an (R)-enantiomer-selective lipase, resulting predominantly in the hydrolysis of the (R)-isomer (at 85% conversion) to give the alcohols 3 with high e.e. Alternatively, hydrolysis of the minor enantiomeric (S)-acetate to approximately 20% conversion left the enriched (R)-configured acetate with improved e.e. (>90%). The moderate enantioselectivities obtained in the catalytic P-C bond formation are enhanced during the enzymatic hydrolysis. Furthermore, availability of the non-racemic phosphonates permits the use of less selective enzymes, resulting in higher yields in comparison with the standard resolution of racemic materials.
Rowe, Bradley J.,Spilling, Christopher D.
p. 1701 - 1708
(2007/10/03)
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