Poly-L-leucine as an added chiral ligand for the palladium catalysed carbonylation of allylic alcohols

Treatment of but-2-en-1-ol with carbon monoxide, oxygen, copper(II) chloride, and hydrochloric acid in tetrahydrofuran containing palladium chloride and poly-L-leucine affords (R)-α-methyl-γ-butyrolactone in 61% enantiomeric excess; (L)-diethyl tartrate and (R)- and (S)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) can also produce the optically active lactone, but in lower optical purity.