Crystal structures of two chiral piperidine derivatives: 1-[(1R)-2-hy­droxy-1-phenyl­eth­yl]piperidin-4-one and 8-[(1S)-1-phenyl­eth­yl]-1,4-dioxa-8-aza­spiro­[4.5]decane-7-thione

The crystal structures of the two title piperidine derivatives show different conformations for the six-membered heterocycle. The N-substituted 4-piperidinone 1-[(1R)-2-hy­droxy-1-phenyl­eth­yl]piperidin-4-one, C(13)H(17)NO(2), (I), has a chair conformation, while the piperidine substituted in position 2 with a thio­carbonyl group, 8-[(1S)-1-phenyl­eth­yl]-1,4-dioxa-8-aza­spiro­[4.5]decane-7-thione, C(15)H(19)NO(2)S, (II), features a half-chair conformation. Comparison of the two structures, and data retrieved from the literature, suggests that the conformational flexibility is mainly related to the hybridization state of the C atom α to the piperidinic N atom: a Csp (3) atom favours the chair conformer, while a Csp (2) atom distorts the ring towards a half-chair conformer. In the crystal structure of (I), weak C—H⋯O hydrogen bonds link the mol­ecules into supra­molecular chains propagating along the b-axis direction. In the crystal of (II), the mol­ecules are linked by weak C—H⋯S contacts into supra­molecular chains propagating along the b-axis direction.