Enantiopure methacrylamide derivative

N-［o-(4-methyl-4

5-dihydro-1

3-oxazol-2-yl)phenyl］ methacrylamide ((S) MeOPMAM) was synthesized and radically polymerized in the presence of rare earth metal trifluoromethanesulfonates (Ln(OTf)3

Ln = La

Nd

Sm

and Y) to yield corresponding optically active polymers.Among these Lewisacids

Y(OTf)3 was found to be most effective for increasing the isotactic specificity during the radical polymerizations when using n-butanol as a solvent.The effect of the Lewis acids was significantly influenced by the ratio of Ln(OTf)3 to monomer and the nature of solvents.The tacticity of polymers was estimated by13C-NMR spectroscopy on the basis of the peak splitting of the quaternary carbon of the main chain (δ=46.5～48.5).The conventional polymerization without Y(OTf)3 produced syndiotacticrich polymer with rr = 67%

while the polymer with a relatively high isotacticity (mm = 47%) was obtained in the case of an equimolar amount of Y(OTf)3 to the monomer.Also

the addition of the rareearth salt increased both the polymer yield and molecular weights.The relationship between the stereoregularity and the chiroptical property as well as the chiral recognition was then examined for the resulting polymers with various tacticities by spectroscopic techniques such as circular dichroism (CD) and NMR.The syndiotacticrich polymer showed a specific rotation of +118.6°; however

the absolute value of ［α］25D decreased with an increase in the isotactic triad content and a negative value (-2.1°) was observed for the polymer having mm = 47%.Correspondingly

the CD intensities at 240 nm and 220 nm were depressed evidently.On the other hand

1H-NMR measurements of the mixture of poly［(S)MeOPMAM］s and racemic 1

1′-bi-2-naphthol (BINOL) were conducted in chloroform-d.The characteristic hydroxyl proton signal of BINOL was split into two peaks ascribed respectively to the levo- and dextro isomer; furthermore

the splitting magnitude appears to be positively correlated with the mm value of the polymers.These results indicate that the polymers containing a higher isotacticity may possess favorable enantioselective discrimination ability toward the target compound.