cis-2-Phenylsulfonyl-12-benzylcyclododecanone, 2-phenylsulfonyl-12-bromocyclododecanone and 2,12-dibenzylcyclododecanone were synthesized though cyclododecanone as raw material, and their structures were confirmed by ¹H NMR, ¹³C NMR spectra and elemental analysis. Crystal data for 4: C₂₅H₃₂O₃S, M_r＝412.57, triclinic, space group P1, a＝0.96531(4) nm, b＝1.12703(5) nm, c＝1.17486(5) nm, α＝89.278(2)°, β＝75.582(2)°, γ＝65.385(2)°, V＝1.11938(8) nm³, D_c＝1.224 g/cm³, Z＝2, F(000)＝444 and m(Mo Kα)＝0.167 mm^－1, S＝1.038. Crystal data for 6: C₁₈H₂₅BrO₃S, M_r＝401.35, triclinic, space group P1, a＝0.77771(16) nm, b＝1.0143(2) nm, c＝1.2040(2) nm, α＝89.46(3)°, β＝80.13(3)°, γ＝75.27(3)°, V＝0.9044(3) nm³, D_c＝1.474 g/cm³, Z＝2, F(000)＝416 and μ(Mo Kα)＝2.400 mm^－1, S＝1.042. The X-ray diffraction analysis of cis-2-phenylsulfonyl-12-benzylcyclododecanone and cis-2-phenylsulfonyl-12-bromocyclododecanone showed that their ring skeleton of cyclododecanone moiety took [3333]-2-one conformation, the smaller substituted group was at α-corner-syn, and the bigger one was at α-side-exo position.

Key words: cis-2,12-bissubstituted cyclododecanone, α-corner-syn-&alpha, -side-exo-bissubstituted[3333]-2-one conformation, preferred conformation, crystal structure