Accordingly, 4-(methylthio)phenyl piperidine-4-carboxylate (4MTPPC) was successfully synthesized in two steps. In the first step, we performed the esterification of Boc-Inp-OH with 4MTP, followed by TFA treatment to remove the Boc group in a second step (Figure ). The product was obtained as a white powder with a good yield (93 %) and satisfactory purity. 4MTP, (Figure ). The signal attributed to the 4MTP methyl group (signal 1, blue) is shifted slightly to higher ppm values due to the introduced ester group. Signals 4 and 6 (blue and green, respectively) are represented with two peaks that most likely arise from the axial and equatorial chair conformation of the piperidine group . The synthesis of polysarcosine was performed by ROP of Sar-NCA monomer according to a well-known method . In contrast to initiation using 4MPT initiation, this approach proved successful. NMR spectra analysis of the resulting polymers shows significant signals attributed to PSar initiated with 4MTPPC initiator. GPC traces of the obtained polymer are narrow, monomodal and are in good agreement with expected values from [M]0/[I]0 data (Mn = 2.9 vs. 3.3 kg/mol). We also tested this initiator using an alternative monomer for polysarcosine synthesis. Synthesis of Sar-NCA requires the use of toxic and harmful chemicals (phosgene or thionyl chloride). Also, the purification, handling and storage of the moisture-sensitive NCA is challenging. To address this, Yamada introduced N-phenyloxycarbonyl amino acids for polypeptide synthesis, which was later adopted by Doriti for polypeptoids. Such monomers can be synthesized in high purity, good yield and stability and polymerized to welldefined polypeptides/polypeptoids.