Synthesis and characterization of stereoregular poly(D-methionyl-L-methionine) and poly(L-methionyl-D-methionyl-L-methionine)

By use of a polycondensation procedure free of racemization, stereoregular polymethionines have been synthesized from C-activated D -methionyl-L -methionine and L -methionyl-D -methionyl-L -methionine. The poly(D -methionyl-L -methionine) and poly(L -methionyl-D -methionyl-L -methionine) so prepared are soluble in chloroform and can be purified through dissolution in this solvent and precipitation by ligroin. Poly(D -Met-L -Met)which is obtained in a 25% yield, is about 5000 in average molecular weight. It has no discernible optical activity when examined between 400 and 600 nm in a trifluoroacetic acid solution. Poly(L -Met-D -Met-L -Met) (40% yield, M. W. = 10,000) is an optically active polymer. [α]₄₃₆²⁴ ≈ + 170° for a chloroformic solution (c = 0.2 CHCl₃).