A practical, convergent route to the key precursor to the tetracycline antibiotics.
Kummer, David A.; Li, Derun; Dion, Amelie; Myers, Andrew G.; Chemical science (Royal Society of Chemistry : 2010) 2 (2011) 1710–1718; doi:10.1039/C1SC00303H

data_1515648
_publ_section_title
;
 A practical, convergent route to the key precursor to the tetracycline
 antibiotics.
;
_journal_issue                   9
_journal_name_full
'Chemical science (Royal Society of Chemistry : 2010)'
_journal_page_first              1710
_journal_page_last               1718
_journal_paper_doi               10.1039/C1SC00303H
_journal_volume                  2
_journal_year                    2011
_chemical_absolute_configuration ad
_chemical_formula_sum            'C20 H20 N2 O4'
_chemical_formula_weight         352.38
_space_group_IT_number           19
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2ac 2ab'
_symmetry_space_group_name_H-M   'P 21 21 21'
_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                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   6.4713(2)
_cell_length_b                   12.2439(3)
_cell_length_c                   21.5133(6)
_cell_measurement_reflns_used    39693
_cell_measurement_temperature    100(2)
_cell_measurement_theta_max      66.0
_cell_measurement_theta_min      3.11
_cell_volume                     1704.58(8)
_computing_cell_refinement       'SAINT 7.46A (Bruker-AXS, 2009)'
_computing_data_collection       'APEX2 v2009.3.0 (Bruker-AXS, 2009)'
_computing_data_reduction        'SAINT 7.46A (Bruker-AXS, 2009)'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 2008)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 2008)'
_diffrn_ambient_temperature      100(2)
_diffrn_measured_fraction_theta_full 0.967
_diffrn_measured_fraction_theta_max 0.967
_diffrn_measurement_device_type  'CCD area detector'
_diffrn_measurement_method       'phi and omega scans'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           CuK\a
_diffrn_radiation_wavelength     1.54178
_diffrn_reflns_av_R_equivalents  0.0401
_diffrn_reflns_av_sigmaI/netI    0.0129
_diffrn_reflns_limit_h_max       7
_diffrn_reflns_limit_h_min       -7
_diffrn_reflns_limit_k_max       11
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       25
_diffrn_reflns_limit_l_min       -24
_diffrn_reflns_number            42649
_diffrn_reflns_theta_full        66.46
_diffrn_reflns_theta_max         66.46
_diffrn_reflns_theta_min         4.11
_exptl_absorpt_coefficient_mu    0.792
_exptl_absorpt_correction_T_max  0.8706
_exptl_absorpt_correction_T_min  0.8088
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   sadabs
_exptl_crystal_colour            'pale yellow'
_exptl_crystal_density_diffrn    1.373
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       plate
_exptl_crystal_F_000             744
_exptl_crystal_size_max          0.28
_exptl_crystal_size_mid          0.22
_exptl_crystal_size_min          0.18
_refine_diff_density_max         0.151
_refine_diff_density_min         -0.161
_refine_diff_density_rms         0.032
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.05(15)
_refine_ls_extinction_coef       0.0045(3)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   1.084
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     242
_refine_ls_number_reflns         2922
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.084
_refine_ls_R_factor_all          0.0257
_refine_ls_R_factor_gt           0.0256
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0431P)^2^+0.2931P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0695
_refine_ls_wR_factor_ref         0.0696
_reflns_number_gt                2902
_reflns_number_total             2922
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            c1sc00303h.txt
_cod_data_source_block           RDP
_cod_depositor_comments
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The following automatic conversions were performed:

'_symmetry_cell_setting' value 'Orthorhombic' changed to
'orthorhombic' according to
/usr/data/users/saulius/automatic-downloads/retrospective/RSC/lib/dictionaries/cif_core.dic
dictionary named 'cif_core.dic' version 2.4.2 from 2011-04-26.

Automatic conversion script
Id: cif_fix_values 2281 2013-09-26 08:29:07Z andrius 
;
_cod_original_sg_symbol_H-M      P212121
_cod_database_code               1515648