The Sonogashira-Hagihara polymerization of 3',5'-diiodo-N-alpha-tert-butoxycarbonyl-L-tyrosine methyl ester (1) and 3',5'-diiodo-N-alpha-tert-butoxycarbonyl-O-methyl-L-tyrosine methyl ester (2) with para-diethynylbenzene (3) was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s [poly(1) and poly(2)] with M-n's ranging from 9900 to 15,000 in 80-87% yields. Poly (1) exhibited intense CD signals in DMSO and THF, but did not in CH2Cl2, indicating that it took a predominantly one-handed helical conformation in the former two solvents. On the other hand, there was no evidence for poly(2) to take a helical structure in these solvents. Poly(1) turned the CD sign at 390 nm from plus to minus in DMSO/H2O = 9/1 (v/v) by the addition of NaOH. Alkaline hydrolysis of ester moieties of poly(1) and poly(2) gave the corresponding polymers having carboxy groups [poly(1a) and poly(2a)]. Poly(1a) and poly(2a) increased the CD intensity by the addition of NaOH. (C) 2010 Elsevier Ltd. All rights reserved.