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. 2019 Jul 12;24(14):2548.
doi: 10.3390/molecules24142548.

Dihydrogen Bond in the Aminoborane Complex of a Nicergoline Intermediate

Jan Čejka  1 , Ladislav Cvak  2 , Simona Žižková  3 , Bohumil Kratochvíl  3 , Alexandr Jegorov  2   4
Affiliations

Dihydrogen Bond in the Aminoborane Complex of a Nicergoline Intermediate

Jan Čejka et al. Molecules. .

Abstract

An aminoborane side product from the nicergoline manufacture process was identified by single-crystal X-ray diffraction. As boranes of pharmaceutical molecules are quite rare, the binding potential of the BH3 group was investigated and compared with similar compounds using Cambridge Structural Database (CSD). Surprisingly, the packing was stabilized by a dihydrogen bond, which triggered a false alert for too-short contact of hydrogen atoms in IUCR checkCIF. As the dihydrogen bond concept is not widely known, such an alert might mislead crystallographers to force -CH3 optimal geometry to -BH3 groups. The B-H distances equal to or less than 1.0 Å (17% of the CSD structures) are substantially biased when analyzing the structures of aminoborane complexes in CSD. To conduct proper searching, B-H bond length normalization should be applied in the CSD search.

Keywords: CSD; X-ray structure; aminoborane; dihydrogen bond; nicergoline; single crystal.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Scheme of nicergoline (1), ester (2), and alcohol (3-MeLuol) intermediates.
Figure 2
Figure 2
Scheme of BH3-MeLuol complex (4) and Luol (5).
Figure 3
Figure 3
ORTEP drawing of BH3-MeLuol (4) with atomic numbering, ADP drawn at 50% probability level.
Figure 4
Figure 4
Parallel-oriented molecules of Luol derivatives. BH3-MeLuol (4)—blue, Luol (5)—red, MeLuol (3)—green, boron—pink.
Figure 5
Figure 5
Side-oriented fitted molecules of Luol derivatives. BH3-MeLuol (4)—blue, Luol (5)—red, MeLuol (3)—green, boron—pink.
Figure 6
Figure 6
Histograms of bond lengths for all B–H bonds (left) and B–H bonds in probably refined BH3 groups (right).
See this image and copyright information in PMC

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