Herein, we report the application of a benzyloxy-functionalized malonic acid half thioester as an activated ester equivalent in a highly enantioselective decarboxylative glycolate aldol reaction. This robust method operates at ambient temperature, tolerates air and moisture, and generates CO2 as the only byproduct. The synthetic applicability of the method is demonstrated by the large-scale enantiodivergent synthesis of α-benzyloxy-β-hydroxybutyric acid thioester and its subsequent conversion to diverse polyoxygenated building blocks, deoxy-sugars, and (-)-angiopterlactone B.