We then turned our attention to screening a variety of chiral thiols derived from both peptides and carbohydrates to supplement our initial examination of C1 (Table 4, entry 1). With peptide-derived catalysts, the thiol source was primarily derived from incorporation of cysteine (Table , entries 2-4). Unfortunately, these cysteine catalysts provided minimal enantioinduction. Based on our previous finding that achiral disulfides were competent precatalysts, we compared a corresponding chiral disulfide/free thiol pair (Table , entries 4-5). Chiral disulfide C5 does generate product, a finding which agrees with our mechanistic work utilizing disulfides in the racemic system, but with reduced yields and minimal enantioinduction. We also tested a peptide containing an aromatic thiol (C6) rather than a cysteine, given its increased similarity to PhSH; however, it did not furnish appreciable enantioinduction (Table ). Additional screening of other peptide catalysts is available in the SI.