title: Structure of a key intermediate in the synthesis of (-)-5-carboxytetrahydroalstonine and (-)-tetrahydroalstonine.
abstract: Methyl [4aS*-(4 alpha,4a beta,7 beta,13b beta,14a beta)]-7,8,13,13b,14,14a- hexahydro-4-methyl-5-oxo-4H-indolo-[2,3-a]pyrano[3,4-g]qu inolizine-7-carboxylate acetone solvate, C22H22N2O4.C3H6O, Mr = 424.50, triclinic, P1, a = 9.9955(13), b = 10.8523(14), c = 11.9352(14) A, alpha = 63.189(9), beta = 72.286(9), gamma = 72.901(10) degrees, V = 1081.8(2) A3, Z = 2, Dx = 1.30 g cm-3(198K), mu = 0.8554 cm-1, Mo K alpha radiation, lambda = 0.7107 A, F(000) = 452, T = 198 K, R = 0.0435 for 3842 reflections, FO greater than or equal to 4 sigma (FO). The acetone solvent is hydrogen bonded to the indole NH group with relevant parameters: N13...O1A 2.982(2), H13...O1A 2.10(2) A, N--H...O 164(2) degrees. The conformation at the C and D ring junction is quasi-cis [relevant torsion angles are C7--N6--C13B--C13A 9.4(2) degrees and C5--N6--C13B--C14 46.7(2) degrees] while the conformation at the D and E ring junction is cis [relevant torsion angles are 37.8(2) degrees for C5--C4A--C14A--C14 and 41.3(2) degrees for C4--C4A--C14A--C1].
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
authors.forename: V M
authors.initials: VM
authors.lastname: Lynch
authors.forename: J W
authors.initials: JW
authors.lastname: Corbett
authors.forename: S F
authors.initials: SF
authors.lastname: Martin
authors.forename: B E
authors.initials: BE
authors.lastname: Davis
mesh_terms: D015394:Molecular Structure; D046948:Secologanin Tryptamine Alkaloids; D014961:X-Ray Diffraction; D015016:Yohimbine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D046948:Secologanin Tryptamine Alkaloids; C068786:5-carboxytetrahydroalstonine; D015016:Yohimbine; C005709:raubasine