Crystal structure of limonoid TS3, isolated fromTrichilia rubescens

Abstract

The title limonoid compound, C26H28O5·0.5H2O (TS3) [systematic name: (3aS,3bS,4aS,5aS,6S,7aR,8aR,8bS,11aR)-6-(furan-3-yl)-3a,5a,8b,11a-tetramethyl-3a,4a,5,5a,6,7,7a,8b,11,11a-decahydrooxireno[2′,3′:4b,5]oxireno[2′′,3′′:2′,3′]cyclopenta[1′,2′:7,8]phenanthro[10,1-bc]furan-3(3aH)-one hemihydrate], crystallizes with two independent molecules (1 and 2) in the asymmetric unit and one water molecule.TS3is composed of three six-membered rings (A,CandD), three five-membered rings (B,EandF) and two epoxide rings. A group of five fused rings (A–E) is bonded to a furan ring (F) with a Csp3—Csp2bond [1.500 (3) Å in molecule 1 and 1.499 (3) Å in molecule 2]. The absolute structures of the molecules in the crystal were determined by resonant scattering; Flack parameter = 0.05 (5). In the crystal, the individual molecules stack in columns along theb-axis direction. The water molecule bridges molecules 1 and 2viaOwater—H...O and C—H...Owaterhydrogen bonds. Together with further C—H...O hydrogen bonds, linking molecules 1 and 2, the columns are linked to form slabs parallel to theabplane. Within each column, molecules are also linkedviaC—H...π interactions involving the five-membered furan (F) rings.