Synthetic studies on β-lactam antibiotics. VII. Mild removal of the benzyl ester protecting group with aluminum trichloride

The benzyl ester protecting group in β-lactam derivatives can be cleanly removed by treatment with aluminum trichloride under mild conditions, preferably in the presence of anisole, to give the corresponding free acids in high yields.     

X-ray crystal structure of a thiabenzene derivative

The first success of an X-ray analysis of a thiabenzene derivative, 1-benzoyl-2-methyl-2-thianaphthalene is described.     

Construction of Helically Stacked π-Electron Systems in Poly(quinolylene-2,3-methylene) Stabilized by Intramolecular Hydrogen Bonds

π-Stacked polymers, which consist of layered π-electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π-stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π-stacked architecture based on poly(quinolylene-2,3-methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo-copolymerization of an o-allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted-tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic-force microscopy.     

Facile synthesis of 8-benzoylthio-2,6-methano-3-benzazocines and 3-benzoylthiomorphinans having small-ring substituents

Synthesis of 3-cyclopropylmethyl-, 3-cyclobutylmethyl-, and 3-methyl-8-benzoylthio-2,6-methano-3-benzazocines (1j-l) was performed by regio-selective chlorosulfonation of non-narcotic 8-deoxy derivatives (1a-c) followed by reduction and benzoylation. 3-Benzoylthiomorphinans (2h-j) were also obtained by the same method. Compounds having small-ring substituents (1k, 1l, 2i, 2j) were found to be weak but pure mu- and delta-opioid antagonists. The analgetic activity of 1k was almost equal to that of pentazocine.     

Synthesis and analgetic activity of sulfur-containing morphinans and related compounds

3-Acylthiomorphinans, 3-carbamoylthio-3-deoxydihydromorphine and 3-benzoylthio-9-aza-17-carbamorphinan were synthesized by Newman-Kwart rearrangement of the corresponding O-thiocarbamates. The analgetic activities were lower than that of pentazocine, and the opioid receptor binding affinities were very weak. These acylthiomorphinans showed low antinociceptive activity compared with corresponding sulfur-containing benzomorphans. 3-Carbamoylthio-deoxydihydromorphine had no significant analgetic activity.