Acetal-initiated Prins bicyclization for the synthesis of hexahydrofuro-[3,4-c]furan lignans and octahydropyrano[3,4-c]pyran derivatives.
Subba Reddy, B. V.; Ramana Reddy, M.; Sridhar, B.; Singarapu, Kiran Kumar; Organic & biomolecular chemistry 12 (2014) 4754–4762; doi:10.1039/c4ob00305e

data_7153948
_publ_section_title
;
 Acetal-initiated Prins bicyclization for the synthesis of
 hexahydrofuro-[3,4-c]furan lignans and octahydropyrano[3,4-c]pyran
 derivatives.
;
_journal_issue                   26
_journal_name_full               'Organic &amp; biomolecular chemistry'
_journal_page_first              4754
_journal_page_last               4762
_journal_paper_doi               10.1039/c4ob00305e
_journal_volume                  12
_journal_year                    2014
_chemical_absolute_configuration ad
_chemical_formula_moiety         'C20 H21 Br O2'
_chemical_formula_sum            'C20 H21 Br O2'
_chemical_formula_weight         373.28
_chemical_name_systematic
; 
(1R,4aS,8S,8aS)-1-(2-bromophenyl)-8-phenyl-octahydropyrano[3,4-c]pyran
;
_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            8
_cell_length_a                   11.2110(12)
_cell_length_b                   16.7616(18)
_cell_length_c                   18.3398(19)
_cell_measurement_reflns_used    6522
_cell_measurement_temperature    294(2)
_cell_measurement_theta_max      23.44
_cell_measurement_theta_min      2.19
_cell_volume                     3446.3(6)
_computing_cell_refinement       'SAINT (Bruker, 2001)'
_computing_data_collection       'SMART (Bruker, 2001)'
_computing_data_reduction        SAINT
_computing_molecular_graphics    'SHELXTL/PC (Sheldrick, 1990)'
_computing_publication_material  SHELXL97
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 2008)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 2008)'
_diffrn_ambient_temperature      294(2)
_diffrn_measured_fraction_theta_full 0.997
_diffrn_measured_fraction_theta_max 0.997
_diffrn_measurement_device       'Bruker SMART APEX CCD area-detector'
_diffrn_measurement_device_type  'CCD Area Detector'
_diffrn_measurement_method       '\w scan'
_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  0.0507
_diffrn_reflns_av_sigmaI/netI    0.0381
_diffrn_reflns_limit_h_max       13
_diffrn_reflns_limit_h_min       -13
_diffrn_reflns_limit_k_max       19
_diffrn_reflns_limit_k_min       -19
_diffrn_reflns_limit_l_max       21
_diffrn_reflns_limit_l_min       -21
_diffrn_reflns_number            31390
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         25.00
_diffrn_reflns_theta_min         1.65
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    2.393
_exptl_absorpt_correction_T_max  0.89
_exptl_absorpt_correction_T_min  0.72
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SABABS; Bruker,2001'
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.439
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       needle
_exptl_crystal_F_000             1536
_exptl_crystal_size_max          0.18
_exptl_crystal_size_mid          0.11
_exptl_crystal_size_min          0.09
_refine_diff_density_max         0.816
_refine_diff_density_min         -0.239
_refine_diff_density_rms         0.050
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.080(8)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.974
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     415
_refine_ls_number_reflns         6049
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      0.974
_refine_ls_R_factor_all          0.0431
_refine_ls_R_factor_gt           0.0344
_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^)+(0.0577P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0881
_refine_ls_wR_factor_ref         0.0912
_reflns_number_gt                5025
_reflns_number_total             6049
_reflns_threshold_expression     I>2\s(I)
_cod_data_source_file            c4ob00305e2.cif
_cod_data_source_block           ar61m
_cod_database_code               7153948