Crystal structure of (1,8-diethyl-1,3,4,9-tetrahydro-pyrano[3,4-b]indol- 1-yl)acetic acid (2-hydroxy-benzylidene)hydrazide, C24H27N3O3

Abstract

Source of materialThe compound, (1,8-diethyl-1,3,4,9-tetrahydro-pyrano[3,4-b]indol-1-yl)acetic acid (2-hydroxy-benzylidene)hydrazide, is obtained from the condensation reaction of (1,8-diethyl-1,3,4,9-tetrahydro-pyrano[3,4-b]indol-1-yl)-acetic acid hydrazide with salicylaldehyde [1,2]. A mixture of 1 g (3.3 mmol) of (1,8-diethyl-1,3,4,9-tetrahydro-pyrano[3,4-b]indol-1-yl)-acetic acid hydrazide, 0.41 g (3.32 mmol) of salicylaldehyde, 50 mL of anhydrous ethanol was vigorously stirred at reflux for 1.5 hours. Then the reaction mixture was filtrated and washed with 30 ml ethanol to give 1.21 g of the title compound (yield 89.9 %). The crystals were obtained from a solution of the compound in anhydrous ethanol after two days at room temperature (m.p. 462-463 K). Experimental detailsThe positions of H1 (at N1), H2 (at N3) and H3 (at O3) were found from Fourier difference maps and refined freely. The other H atoms were placed in calculated positions and allowed to ride on their parent atoms at distances of 0.93 Å 0.97 Å for CH. Isotropic displacement parameters were set at 1.2 to 1.5 times U eq of the parent atom. One ethyl group was found to be disordered over two positions caused by rotation around the C3C16 single bond with approximately equal occupancies. The C17 atom was split into two positions and refined anisotropically. The corresponding H atoms at C16 and C17 were added geometrically in accord with the C16C17A and C16C17B bonds. DiscussionThe title compound is a derivative of the non-steroidal antiinflammatory drugs (NSAIDs) etodolac [3]. Etodolac is an indoleacetic acid derivative with analgesic and limited antiinflammatory properties. Etodolac is rapidly absorbed from the gastrointestinal tract, with a bioavailability of approximately 80 %. Like other NSAIDs, etodolac is highly (more than 99 %) bound to plasma proteins and extensively metabolized in the liver, with a half-life of approximately six to seven hours [4]. Also, gastrointestinal effect is the most common adverse reactions associated with etodolac [5]. In the title crystal structure, the molecules are interlinked by intermolecular hydrogen bonds N3HA···O1 and O1HA···N3 bonds into centrosymmetric dimers. There are two intramolecular hydrogen bonds O3HA···N2, O2HA···N1 forming two closed sixmembered loops in each molecule. The phenyl ring and the pyrrole ring are nearly coplanar. In phenyl ring part, the maximum CC bond length is 1.406(3) Å, the minimum is 1.363(3) Å, and the average CC bond length for the phenyl ring is 1.389(3) Å. In the pyrrole ring part, the longer CC bond is 1.406(3) Å and the other is 1.356(3) Å. The pyran ring has a chair form configuration. Other bond lengths and angles are in normal range.