The conformational preference of some tetrahydropyrrolo[1,2- d][1,3,4]oxadiazine derivatives as studied by NMR spectroscopy and X-ray analysis

Ari Rosling, Karel Klika, Ferenc Fülöp, Reijo Sillanpää, Jorma Mattinen

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The diastereomeric (4S,4aS)- and (4R,4aS)-2,4-diphenyl-4H-4a,5,6,7- tetrahydropyrrolo[1,2-d][1,3,4]oxadiazines and their 2,4,4-triphenyl- substituted analog were synthesised. Their conformational behavior, elucidated by means of NMR spectroscopy and X-Ray analysis, revealed some surprising features. The unsubstituted parent compound (4aS)-2-phenyl-4H- 4a,5,6,7-tetrahydropyrrolo[1,2-d][1,3,4]oxadiazine was shown by X-Ray analysis to adopt the same conformational preference in the solid state as in solution, the cis N-out conformation. However, both (4S,4aS)-2,4-diphenyl-4H- 4a,5,6,7-tetrahydropyrrolo[1,2-d][1,3,4]oxadiazine and its 2,4,4-triphenyl- substituted analog adopted a trans conformation in the solid state, in contrast to their predominant cis conformations adopted in solution. The determination of the conformation in solution required the examination of several parameters including homonuclear NOEs, vicinal H,H and H,C coupling constants, the 2J(H-7α,H-7β) value, the Δδ H-7α,H-7β value, δ H4a, and the 15N chemical shift of the bridgehead nitrogen.

Original languageEnglish
Pages (from-to)2575-2588
Number of pages14
JournalHeterocycles
Volume51
Issue number11
DOIs
Publication statusPublished - Nov 1 1999

ASJC Scopus subject areas

  • Analytical Chemistry
  • Pharmacology
  • Organic Chemistry

Fingerprint Dive into the research topics of 'The conformational preference of some tetrahydropyrrolo[1,2- d][1,3,4]oxadiazine derivatives as studied by NMR spectroscopy and X-ray analysis'. Together they form a unique fingerprint.

  • Cite this