Scheme 1. General conditions effective in the cyclizations of (a) chiral substrates 5a–c and (b) achiral substrate 5c with catalysts 1–4. ^a50 mM phosphate buffer, pH 7.50; ^b100 mM phosphate buffer, pD 8.00; ^c1 : 1 MeOD-d ₄/100 mM phosphate buffer, pD 8.00; ^d1 : 1 MeOD-d ₄/100 mM phosphate buffer, pD 5.00; ^eproduct not observed by ¹H NMR spectroscopy or GC-MS. ^fA single trans product was exclusively formed; the relative stereochemistry at the 1-position (–Me/–nPr) could not be unambiguously determined. Selectivity measurements have an estimated error of ≤3%.