Synthesis and polymerization of racemic and optically active substituted β‐propiolactones. VI. α‐Phenyl β‐propiolactone

Abstract

The synthesis and optical resolution of α‐phenyl β‐amino‐ethylpropionate led to the preparation of optically active α‐phenyl β‐propiolactones (PhPL) of different optical purities. The enantiomeric excess of PhPL was determined using 200 MHz 1H‐NMR spectroscopy, after complexation with tris[3‐(trifluoromethyl hydroxymethylene)‐d‐camphorato]europium III. It was then polymerized, in bulk and in solution, using a potassium acetate/crown ether complex as initiator. The optically active poly(PhPL)s thus obtained are insoluble in most organic solvents, whereas atactic poly(PhPL)s are soluble in CCl4, CHCl3, and dichloroethane. Several differences are observed between the physical properties of optically active and atactic poly(PhPL)s. However, atactic poly(PhPL)s are semi‐crystalline polymers, similar to poly(α‐disubstituted β‐propiolactone)s, but in contrast with poly(α‐methyl β‐propiolactone). Melting (Tf) and glass transition temperatures, as well as enthalpy of fusion (ΔH), vary with the optical purity of the polymers. For example, atactic poly(PhPL) exhibits a Tf = 94°C and ΔH = 9 J/g as compared to Tf = 119°C and ΔH = 37 J/g for a poly(PhPL) having an enatiomeric excess of 50%.

Polymer Synthesis by In Vitro Enzyme Catalysis

“…Lipases in organic media have been used successfully for lactonization of racemic γ-hydroxy esters (4), ω-hydroxy esters (5), and δ-hydroxy esters (6) into enantioenriched γ-butyrolactones (7), ω-lactones (8), and δ-lactones (9), respectively (Schemes 1 and 2). [5][6][7] Enzyme catalysis has generated stereochemical regularity and enantiopurity along chains.…”

“…Chemical routes have shown variable levels of success for the preparation of enantioenriched lactones and their corresponding polymers. Examples of chemically prepared optically active polyesters include poly(α-phenyl-β-propiolactone) ( 15 ), poly(α-ethyl-α-phenyl-β-propiolactone) ( 16 ), , poly(α-meth- yl-α-ethyl-β-propiolactone) ( 17 ), and poly(lactic acid). , Often, the synthetic methods used to prepare enantioenriched monomers either are tedious (requiring multistep reactions) or do not provide the monomer in sufficient enantiopurity. Attempts at carrying out stereoelective polymerizations of racemic lactones using enantiomerically pure polymerization catalysts have often failed to produce useful results.…”

Pt-Catalyzed Rearrangement of Oxaspirohexanes to 3-Methylenetetrahydrofurans: Scope and Mechanism

“…Known β-lactones 9a , b , c , d , f , g , i , m , and n were prepared by literature procedures. Spectral data are in accordance with the literature references.…”

Enzymatic kinetic resolution of tropic acid

“…Poly-3-hydroxyacids are of great interest for bioerodable and biodegradable polymers, 1 while the enantiomeric ratio of the monomers has a dramatic effect on the crystallinity and solubility of the resulting polymer. 2,3 The enzymatic kinetic resolution of 2-arylpropionic acids, mainly ibuprofen, [4][5][6][7][8][9][10][11][12] and related structures, [13][14][15][16][17][18][19] has been studied intensively, but any literature on the enzymatic kinetic resolutions of 2-aryl-3-hydroxycompounds such as tropic acid, is scarce. Only recently, was an enzymatic kinetic resolution of this hydroxy acid utilising lipase PS (Pseudomonas cepacia lipase) to target the primary alcohol reported.…”