Brønsted Acid mediated cyclization of enaminones. Rapid and efficient access to the tetracyclic framework of the strychnos alkaloids.
Edwankar, Rahul V.; Edwankar, Chitra R.; Namjoshi, Ojas A.; Deschamps, Jeffrey R.; Cook, James M.; Journal of natural products 75 (2012) 181–188; doi:10.1021/np200759h

data_1503467
_publ_section_title
;
 Br\/onsted Acid mediated cyclization of enaminones. Rapid and efficient
 access to the tetracyclic framework of the strychnos alkaloids.
;
_journal_issue                   2
_journal_name_full               'Journal of natural products'
_journal_page_first              181
_journal_page_last               188
_journal_paper_doi               10.1021/np200759h
_journal_volume                  75
_journal_year                    2012
_chemical_absolute_configuration syn
_chemical_formula_moiety         'C25 H26 N2 O5'
_chemical_formula_sum            'C25 H26 N2 O5'
_chemical_formula_weight         434.48
_space_group_IT_number           4
_symmetry_cell_setting           monoclinic
_symmetry_space_group_name_Hall  'P 2yb'
_symmetry_space_group_name_H-M   'P 1 21 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 92.005(3)
_cell_angle_gamma                90.00
_cell_formula_units_Z            2
_cell_length_a                   10.9243(19)
_cell_length_b                   7.6452(13)
_cell_length_c                   13.624(2)
_cell_measurement_reflns_used    1408
_cell_measurement_temperature    295(2)
_cell_measurement_theta_max      19.31
_cell_measurement_theta_min      2.35
_cell_volume                     1137.2(3)
_computing_cell_refinement       'Bruker SMART v5.631 (Bruker, 2001)'
_computing_data_collection       'Bruker SMART v5.631 (Bruker, 2001)'
_computing_data_reduction
;
Bruker SAINT v6.45A (Bruker, 2002), Bruker XPREP v6.14 (Bruker, 2001)
;
_computing_molecular_graphics    'Bruker SHELXTL v6.14 (Bruker, 2000b)'
_computing_publication_material  'Bruker SHELXTL v6.14 (Bruker, 2000b)'
_computing_structure_refinement  'Bruker SHELXTL v6.14 (Bruker, 2000b)'
_computing_structure_solution    'Bruker SHELXTL v6.14 (Bruker, 2000b)'
_diffrn_ambient_temperature      295(2)
_diffrn_measured_fraction_theta_full 0.992
_diffrn_measured_fraction_theta_max 0.979
_diffrn_measurement_device_type  'Bruker SMART APEX II CCD'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0386
_diffrn_reflns_av_sigmaI/netI    0.0609
_diffrn_reflns_limit_h_max       13
_diffrn_reflns_limit_h_min       -13
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -9
_diffrn_reflns_limit_l_max       16
_diffrn_reflns_limit_l_min       -13
_diffrn_reflns_number            8368
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         25.56
_diffrn_reflns_theta_min         1.87
_exptl_absorpt_coefficient_mu    0.089
_exptl_absorpt_correction_T_max  0.9973
_exptl_absorpt_correction_T_min  0.9694
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS v2.10 (Bruker, 2000c)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.269
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       'flat rod'
_exptl_crystal_F_000             460
_exptl_crystal_size_max          0.352
_exptl_crystal_size_mid          0.111
_exptl_crystal_size_min          0.03
_refine_diff_density_max         0.138
_refine_diff_density_min         -0.162
_refine_diff_density_rms         0.041
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   1.2(15)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.990
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     294
_refine_ls_number_reflns         4100
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.990
_refine_ls_R_factor_all          0.0873
_refine_ls_R_factor_gt           0.0502
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0633P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1103
_refine_ls_wR_factor_ref         0.1287
_reflns_number_gt                2676
_reflns_number_total             4100
_reflns_threshold_expression     I>2\s(I)
_cod_data_source_file            np200759h_si_002.cif
_cod_data_source_block           cook79
_cod_original_cell_volume        1137.1(3)
_cod_original_sg_symbol_H-M      'P 21'
_cod_database_code               1503467