Preparation and microstructural analysis of poly(lactic‐alt‐glycolic acid)

Abstract

Alternating copolymers of glycolic (G) and lactic (L) acid were prepared by the condensation of the preformed dimers: LLG and LracG. By size exclusion chromatography (THF, PS standards), poly(LLG) exhibited a molecular weight (Mn) of 15.6 kg mol−1, with a weight average molecular weight (Mw) of 26.9 kg mol−1 and a PDI of 1.72. The Mn for poly(LracG) was 9.2 kg mol−1, with a Mw of 12.9 kg mol−1 and a PDI of 1.40. The NMR spectra of poly(LLG) were consistent with an isotactic microstructure. NMR spectra of the racemic poly(LracG) were consistent with an atactic structure. The methylene region of the 1H NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii. Resonances for other groups in both the 1H and 13C NMR spectra gave only a triad level of resolution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4704–4711, 2008

New Insights into Poly(lactic-co-glycolic acid) Microstructure: Using Repeating Sequence Copolymers To Decipher Complex NMR and Thermal Behavior

“…Starting from the previously reported dimer, Bn-LG-SiR 3 , 59 catalytic hydrogenation was used to remove the benzyl group and generate the partially deprotected LG-SiR 3 unit in a 95% yield (Scheme 1). Benzyl ( S )-lactate ( Bn-L ) or benzyl ( R )-lactate ( Bn-L R ) were coupled to LG-SiR 3 to generate di-protected trimers Bn-LLG-SiR 3 and Bn-L R LG-SiR 3 in 84 and 72% yields, respectively.…”

“…While a portion of this work was reported in a previous article, 59 we have since prepared a key member of the series, poly GLGL R , that was not available at the time of that publication.…”

Functional-Group-Tolerant, Nickel-Catalyzed Cross-Coupling Reaction for Enantioselective Construction of Tertiary Methyl-Bearing Stereocenters

“…29 The directing group was installed by a DCC coupling without loss of ee. 23 Cross-coupling of 57 under our optimized reaction conditions afforded the methyl-bearing benzylic stereocenter in 87% yield with 99% es.…”

“…29 DCC coupling appended the necessary leaving group with no loss of ee, providing the starting materials for the transformation. 23 …”

“…39 Enantioselective arylation of aldehyde 48 according to the Bolm strategy furnished the desired enantioenriched alcohol ( R )- 50 in 94% yield and 94% ee. 27b The traceless directing group was then installed by DCC coupling 23 and the substrate was subjected to standard cross-coupling conditions. Diarylethane 53 was obtained in 92% yield with excellent transfer of stereochemical information (97% es).…”