Lipase Catalyzed Enantioselective Transesterification of 5-Acyloxy-2(5H)-Furanones

Several lipases catalyse the transesterification of γ-acyloxyfuranones in organic solvents with high enantioselectivities. This method has been used for the kinetic resolution of 5-acetoxy-2(5H)-furanone, 5-acetoxy-4-methyl-2(5H)-furanone and 5-propionyloxy-2(5H)-furanone, in e.e.’s ranging from 68-98%.

Lipase-Catalyzed Second-Order Asymmetric Transformations as Resolution and Synthesis Strategies for Chiral 5-(Acyloxy)-2(5H)-furanone and Pyrrolinone Synthons

By use of lipase R (Amano, Penicillium roqueforti) immobilized on Hyflo Super Cell it is possible to convert at ambient temperature 5-hydroxy-5H-furan-2-one (5) to acetic acid 5-oxo-2,5-dihydrofuran-2-yl ester (1b) by acylation with vinyl acetate in 1:1 cyclohexane-butyl acetate. At 90% conversion the enantiomeric excess of 1b is 100%. This is an example of an enzyme-catalyzed second-order transformation whereby the unreactive enantiomer of 5 racemizes during reaction, allowing up to 100% conversion and obtainment of high enantiomeric excesses. The method is even more effective with 5-(acyloxy)-2(5H)-pyrrolinones. Racemic acetic acid 1-acetyl-5-oxo-2,5-dihydro-1H-pyrrol-2-yl ester (2) when treated with the lipase from Candida antarctica at ambient temperature in 3:1 n-hexane-butanol undergoes exactly 50% conversion to afford (+)-2 in >99% enantiomeric excess. This is the unreactive enantiomer. The (-)-enantiomer is converted to the 5-hydroxy derivative 6, which with Candida antarctica in 1:1 n-hexane-vinyl acetate at 69 °C (the temperature is higher to increase the rate of racemization) is transformed (100% conversion) to (-)-2, obtained in >99% enantiomeric excess. The scope of these second-order asymmetric transformations is discussed as well as procedures for optimalization of reaction conditions whereby transesterification strategies are combined with those of second-order asymmetric transformation.

Glycan-modified melanoma-derived apoptotic extracellular vesicles as antigen source for anti-tumor vaccination

Tumors that lack T cell infiltration are less likely to respond to immune checkpoint inhibition and could benefit from cancer vaccination for the initiation of anti-tumor T cell responses. An attractive vaccine strategy is in vivo targeting of dendritic cells (DCs), key initiators of antigen-specific T cell responses. In this study we generated tumor-derived apoptotic extracellular vesicles (ApoEVs), which are potentially an abundant source of tumor-specific neo-antigens and other tumor-associated antigens (TAAs), and which can be manipulated to express DC-targeting ligands for efficient antigen delivery. Our data demonstrates that by specifically modifying the glycocalyx of tumor cells, high-mannose glycans can be expressed on their cell surface and on extracellular vesicles derived after the induction of apoptosis. High-mannose glycans are the natural ligands of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), a dendritic cell associated C-type lectin receptor (CLR), which has the ability to efficiently internalize its cargo and direct it to both major histocompatibility complex (MHC)-I and MHC-II pathways for the induction of CD8+ and CD4+ T cell responses, respectively. Compared to unmodified ApoEVs, ApoEVs carrying DC-SIGN ligands are internalized to a higher extent, resulting in enhanced priming of tumor-specific CD8+ T cells. This approach thus presents a promising vaccination strategy in support of T cell-based immunotherapy of cancer