1H, 13C, and 15N NMR stereochemical study of cis-fused 7a(8a)-methyl and 6-phenyl octa(hexa)hydrocyclopenta[d][1,3]oxazines and [3,1]benzoxazines

Petri Tähtinen, Jari Sinkkonen, Karel D. Klika, Ville Nieminen, Géza Stájer, Zsolt Szakonyi, Ferenc Fülöp, Kalevi Pihlaja

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Four 7a-methyl octa(or hexa)hydrocyclopenta[d][1,3]oxazines, five 8a-methyl octa(or hexa)hydro[3,1]benzoxazines, two 6-phenyl hexahydro[3,1]benzoxazinones, and 8a-methyl hexahydro[1,3]benzoxazinone, all cis-fused, were prepared and their stereostructures studied by various one-and two-dimensional 1H, 13C, and 15N NMR spectroscopic methods. In solution, the cyclopentane-fused 2-oxo derivatives and the 1,3-benzoxazinone were found to attain exclusively the N-in/O-in conformation, whereas the 6-phenyl 2-oxo/thioxo derivatives were found to be present predominantly in the N-out conformation. The C-2 unsubstituted and the 2-oxo/thioxo 7a/8a-methyl derivatives were all present in solution as a rapidly interconverting equilibrium of the N-in and N-out conformations. The C-2 methyl derivatives were each found to be interconvertable mixtures of epimers (at C-2) with the N-in conformer predominating for one epimer and the N-out conformer predominating for the other, with both predominating conformers having the C-2 methyl group equatorially orientated. The substituent on the nitrogen (H or Me) was found to be always predominantly equatorial with respect to the heteroring, except for the epimeric 2-methyl derivatives with N-out conformations where steric constraints and the generalized anomeric effect resulted in the axial orientation of the C-2 methyl being favored.

Original languageEnglish
Pages (from-to)187-198
Number of pages12
JournalChirality
Volume14
Issue number2-3
DOIs
Publication statusPublished - Feb 11 2002

Keywords

  • Conformation
  • Epimerization
  • Preparation
  • Saturated heterocycles
  • Substituent effect

ASJC Scopus subject areas

  • Analytical Chemistry
  • Catalysis
  • Pharmacology
  • Drug Discovery
  • Spectroscopy
  • Organic Chemistry

Fingerprint Dive into the research topics of '<sup>1</sup>H, <sup>13</sup>C, and <sup>15</sup>N NMR stereochemical study of cis-fused 7a(8a)-methyl and 6-phenyl octa(hexa)hydrocyclopenta[d][1,3]oxazines and [3,1]benzoxazines'. Together they form a unique fingerprint.

  • Cite this