An efficient route to all stereoisomeric enantiopure 6-amino-3-alkyl-3- azabicyclo[3.2.1]octane-6-carboxylic acids

A single-step synthesis on a gram scale of four pure stereoisomers of the 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylic acid was carried out using (R)-1-phenylethylamine to confer chirality. The phenylethyl group, and the p-methoxy group linked to the N-atom, are easily removed by hydrogenolysis to afford the corresponding NH-3 derivatives. A series of N-3-alkyl compounds were prepared by way of a "one-pot" deprotection-alkylation procedure starting from the above key compounds. Their biological activity has been evaluated on the GABA receptor.     

Cyclization and rearrangement of diterpenoids. VII. Composition of the hydrocarbon fraction of a mixture of the products of cyclization of manool and sclareol by ordinary acids

The hydrocarbon fractions of the products of the cyclization of manool and sclareol by a mixture of conc. sulfuric and formic or acetic acids have been investigated. It has been established that they contain, in addition to the ⁸/⁹-pimaradiene, ⁸(⁹)-isopimaradiene, roasadiene, and 13-epirosadiene identified previously, the tetracyclic hydrocarbons (1R, 2S, 7S, 11S, 12R, 13R)-2, 6, 6, 11, 13-pentamethyl-tetracyclo [10.2.1.0^1.10.0^2.7] pentadeca-9-ene and (1S, 2R, 11S, 12R, 1R)-2, 7, 7, 11, 15-pentamethyltetracyclo[10.2.1.0^2.11.0^3.8] pentadeca(8)-ene.Institute of Chemistry of the Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinii, No. 5, pp. 719–721, September–October, 1988.     

Macrocyclic Tetramers—Structural Investigation of Peptide-Peptoid Hybrids

Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class.     

Direct metalation of methoxymethyl arylmethyl ethers: A tin-free approach to the generation of α-alkoxyalkoxy-substituted aryllithiums

The generation of a series of α-methoxymethoxy-substituted arylmethyllithiums was achieved by direct metalation of the corresponding arylmethyl methoxymethyl ethers. While the effect of substituents at the benzylic position is straightforward, substituents located on the aromatic ring promote the set up of a competition between lateral and aromatic metalation, strongly affected by the position and relative ortho directing properties of the new substituent. The proposed methodology allows a simple approach to the generation of a wide array of functionalized organolithium reagents.