Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

• Raju Cheerlavancha,
• Ahmed Ahmed,
• Yun Cheuk Leung,
• Aggie Lawer,
• Qing-Quan Liu,
• Marina Cagnes,
• Hee-Chan Jang,
• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

• (right) has a bent shape which provides gauche alignments between all pairs of vicinal C–F and C–N bonds, whilst avoiding any 1,3-dipolar repulsions [11][12][43]. The observed J values for the all-syn trifluoro amino acid 6b also allowed its solution conformation to be deduced (Figure 2). The J values

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• through nOe (Figure 6a). In 4, nOe was observed among H(4)ax, H(5)eq, and H(2)ax, and for H(7)ax with H(6)eq and H(8)eq. Furthermore, nOe was observed among H(5)eq, H(6)ax, and H(6)eq (Figure 6b). Based on the nOe values and 3JH,H coupling constants, the solution conformation was determined using the

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

• Fátima M. P. de Rezende,
• Marilua A. Moreira,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2012, 8, 1227–1232, doi:10.3762/bjoc.8.137

• steric effect, but it suppresses adventitious metabolism, influences the pKa of functional groups, and alters solution conformation [12]. In this context, conformational screening and theoretical evaluation of 2-fluorobicyclo[2.2.1]heptan-7-ols (2-fluoronorbornan-7-ols, compounds 5–8 in Figure 1

Inversion symmetry and local vs. dispersive interactions in the nucleation of hydrogen bonded cyclic n-mer and tape of imidazolecarboxamidines

• Sihui Long,
• Venkatraj Muthusamy,
• Peter G. Willis,
• Sean Parkin and
• Arthur Cammers

Beilstein J. Org. Chem. 2008, 4, No. 23, doi:10.3762/bjoc.4.23

• related to the coordinates involving one dihedral angle and hydrogen bonding. The results establish a connection between solution and solid phase conformation. Keywords: counterpoise; crystal engineering; packing motif; solution conformation; Wallach's rule; Introduction Bonding in organic compounds and

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• are considered (Figure 4). It is not obvious from the NMR data which of a or b is the favoured solution conformation for the erythro isomer. We infer a significant contribution from rotamer b where the C-H bonds are gauche on the basis of the small 3JHH value (2.6 Hz), however the relatively small

• ). For the threo- 21 isomer, there are two vicinal 3JHF couplings of similar and large magnitude (26.3 and 23.6 Hz) suggesting that rotamer d, with two trans 3JHF relationships and again with the fluorines gauche, is the most significant contributor to the solution conformation. In the solid state