Repeating sequence copolymers of poly(lactic‐co‐caprolactic acid) (PLCA), poly(glycolic‐co‐caprolactic acid) (PGCA), and poly(lactic‐co‐glycolic‐co‐caprolactic acid) (PLGCA) have been synthesized by polymerizing segmers with a known sequence in yields of 50–85% with Mns ranging from 18–49 kDa. The copolymers exhibited well‐resolved NMR resonances indicating that the sequence encoded in the segmers used in their preparation is retained and that transesterification is minimal. The exact sequences allowed for unambiguous assignment of the NMR spectra, and these standards were compared with the data previously reported for random copolymers. The glass transition temperatures (Tgs) of the PLCA and PGCA copolymers were found to depend primarily on monomer ratio rather than sequence. Sequence dependent Tgs were, however, noted for the PLGCA polymers with 1:1:1 L:G:C ratios; poly LGC and poly GLC exhibited Tgs that differed by nearly 8 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Naturally occurring glycopeptides and glycoproteins play important roles in biological processes. Glycosylation is one of the most common post-translational modifications in vivo. Glycopeptides are involved in cell signaling and sorting, providing cell surface markers for recognition. From the drug design and synthesis perspective, modification of a peptide through glycosylation results in increased bioavailability and bioactivity of glycopeptides in living systems with negligible toxicity of degradation products. Glycopeptide synthesis can be accomplished through incorporation of a glycosylated amino acid in solid phase peptide synthesis (SPPS) to form the desired peptide, or via incorporation of sugar-amino acid moieties. Additionally, research indicates that glycosylation increases penetration of the blood-brain barrier (BBB) by peptides, which may lead to novel therapeutics for neurological disorders. Recent applications of glycopeptides have focused on the in vivo central nervous system (CNS) effects after peripheral administration of centrally active peptides modified with various carbohydrates.

Here we report a method for the preparation of anomerically pure β-S-glycopyranosides (1,2-trans-glycosides) from the corresponding peracetate donors. S-glycosylation was performed in CHCl3 at reflux in the presence of a catalytic amount of InBr3. Deacylation of the intermediate peracetates were achieved under Zemplén conditions. Five pyranose examples, monosaccharides D-glucose and D-galactose and disaccharides cellobiose, maltose, and lactose, were used as donors, and five thiols including an α/ω dithiol and Fmoc-L-cysteine were used as acceptors. Melting points, high res MS, [α]D and NMR data ((1)H and (13)C, including COSY, HSQC and HMBC) are reported for compounds not previously described.

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