Reductive decarboxylation with zinc-copper

Chiral 4-hydroxy-2-cyclopentenones. Both (R)- and (S)-4-hydroxy-2-cyclo-pentenones can be obtained from phenol. The first step is alkaline hypochlorite oxidation to the acid 1, which is resolved with brucine. Oxidative decarboxylation of 1 gives 2, which is partially dechlorinated and protected as the silyl ether (3). The last step to 4 is reduction with zinc-silver (S, 760) or zinc-copper. ... 

In addition to the desired product, route C produces hydrogen, sodium chloride and additional ammonia (from quenching of the sodium amide with ammonium chloride), zinc and copper hydroxides from the reduction (for simplicity we will assume one mole of each, and no other by-products), one third of a mole of phosphorous acid, sodium bromide, ethanol (from the ester hydrolysis) and carbon dioxide (from the decarboxylation). The molecular weights involved are therefore 126, 1,... 

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