Abstract
The structure of the title compound, C32H51NO6, was determined from 62-year-old crystals at room temperature and refined with 100 K data in a monoclinic (C2) space group. This compound with a triterpenoid structure, now confirmed by this study, played an important role in the determination of the structure of lanosterol. The mol-ecules pack in linear O-H⋯O hydrogen-bonded chains along the short axis (b), while parallel chains display weak van der Waals inter-actions that explain the needle-shaped crystal morphology. The structure exhibits disorder of the flexible methyl-heptane chain at one end of the main mol-ecule with a small void around it. Crystals of the compounds were resistant to data collection for decades with the available cameras and Mo Kα radiation single-crystal diffractometer in our laboratory until a new instrument with Cu Kα radiation operating at 100 K allowed the structure to be solved and refined.
Highlights
The structure of the title compound, C32H51NO6, was determined from 62-yearold crystals at room temperature and refined with 100 K data in a monoclinic (C2) space group
Crystals of the compounds were resistant to data collection for decades with the available cameras and Mo K radiation single-crystal diffractometer in our laboratory until a new instrument with Cu K radiation operating at 100 K allowed the structure to be solved and refined
Falco (1922–2015) in 1952 after a spectroscopic structure determination (Falco et al, 1952) that was relevant for the correct determination of the structure of lanosterol (Eschenmoser et al, 1955) and were handed in the glass vial shown in Fig. 1 to Professor R
Summary
Crystals of the title compound were obtained by Professor M. In this table we find that C3A and C7A (bridgehead atoms in the benzazepine bicycle) C7B and C12B (bridgehead atoms of the fused azepine and indene groups) and C9A (bridgehead atom in the indene bicycle) display unusual bond distances [long C3A—C7A = 1.584 (4), C7B—C8 = 1.580 (4), C7B—C12B = 1.578 (4) Aand short C9—C9A = 1.500 (4) A ] and C7B, C9A and C12A show unusual bond angles [low O7—C7B—C8 = 97.7 (2), C12A— C9A—C9 = 102.5 (2), C12—C12A—C9A = 101.1 (2)] in addition to other unusual features Another significant contribution to the strain in this region of the molecule is the diketone group C7B—C8( O8)— C9( O9)—C9A that shows an elongated Csp2—Csp bond [C8—C9 of 1.549 (5) A ] and a large O8—C8—C9—O9 torsion angle of À43.7 (5). The large unit cell, the presence of positional disorder (aggravated at room temperature) and voids in the crystal structure, combined with the C, H, N and O composition of the crystals explain the poor scattering power that prevented structure determination with older instruments
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