31556-74-8Relevant articles and documents
-
Hashimoto,S. et al.
, p. 2907 - 2908 (1977)
-
Regioselective Asymmetric Alkynylation of N-Alkyl Pyridiniums
Grigolo, Thiago A.,Subhit, Ariana R.,Smith, Joel M.
supporting information, p. 6703 - 6708 (2021/09/08)
Disclosed in this Letter is a novel asymmetric addition of alkynyl nucleophiles to N-alkylpyridinium electrophiles. The coupling is effected under mild and simple reaction conditions, affording dihydropyridine products with complete regiochemical and stereochemical control. In addition to several manipulations of the dihydropyridine products, the utility of this transformation is demonstrated through a concise, dearomative, and asymmetric synthesis of (+)-lupinine, a natural acetylcholine esterase inhibitor.
Preferred conformations of peptides containing tert-leucine, a sterically demanding, lipophilic α-amino acid with a quaternary side-chain C β atom
Formaggio, Fernando
, p. 2395 - 2404 (2007/10/03)
Terminally protected homopeptides of tert-leucine, from the dimer to the bexamer, co-oligopeptides of tert-leucine in combination with α-aminoisobutyric acid or glycine residues up to the hexamer level, and simple dipeptides representing known scaffolds for catalysts in asymmetric organic reactions were prepared by solution methods and fully characterized. The results of conformation analysis, performed by use of FT-IR absorption, NMR, CD, and X-ray diffraction techniques, indicate that this Hydrophobic α-amino acid with tetrasubstitution at the Cβ atom is structurally versatile. We show that it prefers extended or semiextended conformations, but can also be accommodated in folded structures, pro vided that these are biased by the presence of helicogenic residues. The current large-scale production of Tle, combined with its conformational preferences unravelled in this work, should make this bulky, hydrophobic, C α-trisubstituted α-amino acid a regular building block of any strategy seeking to tailor peptides with improved catalytic and pharmacological properties.
