Reaction of caprolactams with an axial ester substituent with base gives the 6-azabicyclo-[3.2.1]octane ring system via Dieckmann cyclization.

Lactams are an important class of heterocyclic compounds and are widely used for industrial and pharmaceutical purposes. Even decades after initial lactam syntheses, research on their physical and chemical properties is still rewarding. It delivers valuable information on the reactivity of lactams and their conformational behavior. For the small- and medium-sized parent lactams, the X-ray structures have been well-known, except for the “missing link”, the six-membered valerolactam. An X-ray structure of valerolactam is described here for the first time, stimulating a comparative discussion of the homologous lactam series. The experimental solid state conformation of valerolactam differs significantly from the calculated and energy-minimized ones reported in the literature. The amide bond length in valerolactam is more or less equal to that in other lactams. A comparison with the structure of cyclohexene revealed striking similarities arising from the partial C–N double bond in valerolactam caused by amide resonance.

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Highlights1. Thermolabile NPS can generate artefacts in the traditional GC-MS analysis 2. When analysed by GC, 25I-NBOH fragments into 2C-I and an ortho-phenolic benzyl ether (o-PBE) 3. No method adjustments can refrain 25I-NBOH thermo degradation on GC analysis 4. DSC and TGA analysis clarify 25I-NBOH´s thermal instability 5. Derivatization can overcome 25I-NBOH degradation in the GC-MS

Synthesis and enzymatic evaluation of new series of N 4 -substituted piperazine naphthamide derivatives as BACE-1 inhibitors for the treatment of Alzheimer's disease are reported.

In this paper a series of simple lactam esters and carboxylic acids is studied with respect to their overall conformation and hydrogen bonding patterns. In total, eight lactams featuring Nαsubstitution have been synthesized. Additionally, the molecular structures of related lactam esters have been considered. The length of the amide bonds does not seem to be majorly influenced by different substituents unless the electron withdrawing N-Boc-protection group is introduced, resulting in a higher susceptibility towards hydrolytic ring opening. As known from other lactams, the Nα ester moiety of the title compounds can be in an axial or equatorial conformation. Smaller ester groups were found to prefer equatorial positions, while larger ones occupy axial sites. N-substitution seems to promote axial conformations of the respective Nα group, with enantholactams being the only studied exception. In addition to the two common amide packing motifs, i.e. the R 2 2 (8) amide dimer (NH•••O/NH•••O) and the C(4) amide chain, a third graph-set was found: the R 2 2 (8) NH•••O/CH•••O=C heterodimer. In general, there seems to be a tendency for medium-sized lactams as well as lactams with small esters to form R 2 2 (8) amide dimers. Larger esters and enantholactam esters lead to C(4) amide chains. In this respect the formation of R 2 2 (8) N-H•••O/C-H•••O=C heterodimers should be seen as a remarkable exception.

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The crystal structures of two bispyridyl ketones featuring either two methyl residues or one methyl and one bromomethyl residue, respectively, are presented. In order to elucidate the influence of the substituents, a comprehensive comparison with the non-methylated mother compound has been performed. A special focus lies thereby on the relative position of the heteroatoms and their free electron pairs. The two methyl groups at the bispyridyl ketone result in two molecules in the asymmetric unit adopting rather different conformations. Due to the fast crystallization conditions and a melting point differing from the literature, a polymorph close to a local minimum in the energy hypersurface seems possible. After introducing a bromine atom to one of the two methyl groups, the molecular conformation is very similar to the unsubstituted molecule. The packing of both title compounds is dominated by weak contacts of the C–H⋯π and C–H⋯Y type (Y = O, N) and C–H⋯Br- and Br⋯π-contacts for the brominated molecule