A surprising steric effect on a tandem cycloaddition/ring-opening reaction: rapid syntheses of difluorinated analogues of (hydroxymethyl)conduritols.
Fawcett, John; Moralee, Andrew C; Percy, Jonathan M; Salafia, Vittoria; Vincent, Mark A; Hillier, Ian H; Chemical communications (Cambridge, England)  (2004) 1062–1063; doi:10.1039/b401245c

data_7102621
_publ_section_title
;
 A surprising steric effect on a tandem cycloaddition/ring-opening
 reaction: rapid syntheses of difluorinated analogues of
 (hydroxymethyl)conduritols.
;
_journal_issue                   9
_journal_name_full               'Chemical communications (Cambridge, England)'
_journal_page_first              1062
_journal_page_last               1063
_journal_paper_doi               10.1039/b401245c
_journal_year                    2004
_chemical_formula_sum            'C20 H18 Br2 F4 O12'
_chemical_formula_weight         686.16
_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                 94.404(2)
_cell_angle_gamma                90.00
_cell_formula_units_Z            2
_cell_length_a                   7.0091(8)
_cell_length_b                   11.5134(13)
_cell_length_c                   14.9095(17)
_cell_measurement_reflns_used    5017
_cell_measurement_temperature    150(2)
_cell_measurement_theta_max      27.18
_cell_measurement_theta_min      2.24
_cell_volume                     1199.6(2)
_computing_cell_refinement       'Bruker SMART'
_computing_data_collection       'Bruker SMART'
_computing_data_reduction        'Bruker SAINT'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      150(2)
_diffrn_measured_fraction_theta_full 0.997
_diffrn_measured_fraction_theta_max 0.997
_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           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0236
_diffrn_reflns_av_sigmaI/netI    0.0319
_diffrn_reflns_limit_h_max       8
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       13
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       17
_diffrn_reflns_limit_l_min       -16
_diffrn_reflns_number            8057
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         25.00
_diffrn_reflns_theta_min         1.37
_exptl_absorpt_coefficient_mu    3.474
_exptl_absorpt_correction_T_max  0.716
_exptl_absorpt_correction_T_min  0.444
_exptl_absorpt_correction_type   empirical
_exptl_absorpt_process_details
;
absorption correction based on 6846 reflections (SADABS); Rint 0.077 before
correction and 0.039 after.
;
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.900
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       block
_exptl_crystal_F_000             680
_exptl_crystal_size_max          0.43
_exptl_crystal_size_mid          0.38
_exptl_crystal_size_min          0.33
_refine_diff_density_max         0.474
_refine_diff_density_min         -0.357
_refine_diff_density_rms         0.068
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.328(8)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.993
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     348
_refine_ls_number_reflns         4055
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.993
_refine_ls_R_factor_all          0.0314
_refine_ls_R_factor_gt           0.0294
_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^)+(0.0458P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0702
_refine_ls_wR_factor_ref         0.0708
_reflns_number_gt                3792
_reflns_number_total             4055
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            b401245c_cif.txt
_cod_data_source_block           9
_cod_depositor_comments
;
The following automatic conversions were performed:
'_symmetry_cell_setting' value 'Monoclinic' changed to 'monoclinic'
according to '/home/saulius/struct/CIF-dictionaries/cif_core.dic'
dictionary named 'cif_core.dic' version 2.4.1 from 2010-06-29.

Automatic conversion script
Id: cif_fix_enum 1527 2010-12-29 10:47:43Z saulius 
;
_cod_original_sg_symbol_H-M      P2(1)
_cod_database_code               7102621