Isosorbide is a stiff bicyclic diol derived from glycose-based polysaccharides, and is thus an attractive building block for novel rigid bioplastics. In the present work, a highly regioselective biocatalytic approach for the synthesis of isosorbide 5-methacrylate was developed. The Lipozyme RM IM (Rhizomucor miehei lipase)-catalyzed process is straightforward, easily scalable, and chromatography-free; a simple extractive workup afforded the monomer at >99% purity and in 87% yield. The developed strategy was applied for the synthesis of a series of monomethacrylated isosorbide derivatives. Radical polymerization of the monomers produced rigid polymethacrylates with a certain side group in either endo or exo configuration, exclusively, which generated materials with great diversity of properties. For example, the two regioisomeric polymers carrying hydroxyl groups reached a glass transition temperature at T g = 167 °C. The polymer tethered with dodecanoate chains in exo position showed crystallinity with an unexpectedly high melting point at T m = 83 °C. In contrast, the corresponding sample with dodecanoate chains in endo positions was fully amorphous with T g = 54 °C. Efficient biocatalytic synthesis combined with attractive polymer properties opens possibilities for production of these biobased polymers on an industrial scale.

Conversion of biobased platform chemicals to enantiopure compounds has become topical. We report a straightforward synthesis of 4-(acyloxy)-pentanoic acids from γ-valerolactone (GVL). An alkaline hydrolysis of GVL is followed by a stereoselective lipase-catalyzed acylation of the sodium salt. Acidic hydrolysis of the acylation product affords (R)-4-(acyloxy)­pentanoic acid and relactonized (S)-GVL. (R)-4-(Propionyloxy)­pentanoic acid and (R)-GVL are obtained with e.r. > 99/1. An additional enzymatic step following a slightly modified process affords (S)-4-(acetyloxy)­pentanoic acid with e.r. > 99/1. Simple access to enantiopure 4-(acyloxy)­pentanoic acids will stimulate the development of their novel applications, including biobased isotactic polymers.

We have prepared a series of 12 d -isosorbide-2-alkanoate-5-methacrylate monomers as single regioisomers with different pendant linear C2–C20 alkanoyl chains using biocatalytic and chemical acylations. By conventional radical polymerization, these monomers provided high-molecular-weight biobased poly(alkanoyl isosorbide methacrylate)s (PAIMAs). Samples with C2–C12 alkanoyl chains were amorphous with glass transition temperatures from 107 to 54 °C, while C14–C20 chains provided semicrystalline materials with melting points up to 59 °C. Moreover, PAIMAs with C13–C20 chains formed liquid crystalline mesophases with transition temperatures up to 93 °C. The mesophases were studied using polarized optical microscopy, and rheology showed stepwise changes of the viscosity at the transition temperature. Unexpectedly, a PAIMA prepared from a regioisomeric monomer (C18) showed semicrystallinity but not liquid crystallinity. Consequently, the properties of the PAIMAs were readily tunable by controlling the phase structure and transitions through the alkanoyl chain length and the regiochemistry to form fully amorphous, semicrystalline, or semi/liquid crystalline materials.

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