Elusive π-helical peptide foldamers spotted by chiroptical studies.
Di Silvio, Sergio; Bologna, Fabio; Milli, Lorenzo; Giuri, Demetra; Zanna, Nicola; Castellucci, Nicola; Monari, Magda; Calvaresi, Matteo; Górecki, Marcin; Angelici, Gaetano; Tomasini, Claudia; Pescitelli, Gennaro; Organic & biomolecular chemistry 18 (2020) 865–877; doi:10.1039/c9ob02313e

data_7157301
_publ_section_title
;
 Elusive \p-helical peptide foldamers spotted by chiroptical studies.
;
_journal_issue                   5
_journal_name_full               'Organic &amp; biomolecular chemistry'
_journal_page_first              865
_journal_page_last               877
_journal_paper_doi               10.1039/c9ob02313e
_journal_volume                  18
_journal_year                    2020
_chemical_absolute_configuration syn
_chemical_formula_sum            'C20 H26 N2 O6'
_chemical_formula_weight         390.43
_space_group_crystal_system      tetragonal
_space_group_IT_number           78
_space_group_name_Hall           'P 4cw'
_space_group_name_H-M_alt        'P 43'
_atom_sites_solution_hydrogens   mixed
_audit_creation_method           SHELXL-2014/7
_audit_update_record
;
2019-02-13 deposited with the CCDC.	2019-12-10 downloaded from the CCDC.
;
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   10.5551(8)
_cell_length_b                   10.5551(8)
_cell_length_c                   18.9321(14)
_cell_measurement_reflns_used    9902
_cell_measurement_temperature    296(2)
_cell_measurement_theta_max      28.24
_cell_measurement_theta_min      2.73
_cell_volume                     2109.2(3)
_computing_cell_refinement       'Bruker SAINT'
_computing_data_collection       'Bruker APEX2'
_computing_data_reduction        'Bruker SAINT'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL'
_computing_structure_refinement  'SHELXL-2014 (Sheldrick 2014)'
_computing_structure_solution    'SHELXS-97 (Sheldrick 2008)'
_diffrn_ambient_temperature      296(2)
_diffrn_measured_fraction_theta_full 0.996
_diffrn_measured_fraction_theta_max 0.993
_diffrn_measurement_device_type  'Bruker APEX-II CCD'
_diffrn_measurement_method       '\f and \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0399
_diffrn_reflns_av_unetI/netI     0.0283
_diffrn_reflns_Laue_measured_fraction_full 0.996
_diffrn_reflns_Laue_measured_fraction_max 0.993
_diffrn_reflns_limit_h_max       14
_diffrn_reflns_limit_h_min       -14
_diffrn_reflns_limit_k_max       14
_diffrn_reflns_limit_k_min       -14
_diffrn_reflns_limit_l_max       25
_diffrn_reflns_limit_l_min       -25
_diffrn_reflns_number            32476
_diffrn_reflns_point_group_measured_fraction_full 0.993
_diffrn_reflns_point_group_measured_fraction_max 0.986
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         28.311
_diffrn_reflns_theta_min         2.209
_exptl_absorpt_coefficient_mu    0.091
_exptl_absorpt_correction_T_max  0.987
_exptl_absorpt_correction_T_min  0.956
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   SADABS
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.229
_exptl_crystal_description       block
_exptl_crystal_F_000             832
_exptl_crystal_size_max          0.30
_exptl_crystal_size_mid          0.25
_exptl_crystal_size_min          0.22
_refine_diff_density_max         0.226
_refine_diff_density_min         -0.220
_refine_diff_density_rms         0.064
_refine_ls_abs_structure_details
;
 Flack x determined using 1370 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
;
_refine_ls_abs_structure_Flack   0.3(3)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.034
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     249
_refine_ls_number_reflns         5178
_refine_ls_number_restraints     2
_refine_ls_restrained_S_all      1.035
_refine_ls_R_factor_all          0.0914
_refine_ls_R_factor_gt           0.0654
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.1069P)^2^+0.2437P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1686
_refine_ls_wR_factor_ref         0.1841
_reflns_Friedel_coverage         0.930
_reflns_Friedel_fraction_full    0.989
_reflns_Friedel_fraction_max     0.979
_reflns_number_gt                3720
_reflns_number_total             5178
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            c9ob02313e2.cif
_cod_data_source_block           shelx
_cod_depositor_comments
'Adding full bibliography for 7157301--7157302.cif.'
_cod_original_cell_volume        2109.2(4)
_cod_database_code               7157301
_shelx_shelxl_version_number     2014/7
_shelx_res_checksum              53997