Application of long range j c-h resolved 2d spectroscopy (lrjr) in structural elucidation of natural products. The structure of oxirapentyn

✍ Scribed by Haruo Seto; Kazuo Furihata; Noboru Otake; Yasuhiro Itoh; Shuji Takahashi; Tatsuo Haneishi; Muneki Ohuchi

• Publisher: Elsevier Science
• Year: 1984
• Tongue: French
• Weight: 288 KB
• Volume: 25
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)99877-0

✦ Synopsis

The structure of a fungal metabolite, oxyrapentyn has been determined as shown in Fig. by application of a new NMR technique, long range J C-H resolved 2D spectroscopy (LRJR). One of the problems in the structural elucidation of complicated molecules by NMR spectroscopy is how to connect proton spin systems separated by quaternary carbons or heteroatoms. This problem has been partly solved by 'H-NMR NOE experiment and/or 13C-{1Hl long range selective proton decoupling (LSPD)'). Although the latter method is very useful in case of aromatic or saturated systems, in which carbon signals to be observed are coupled to a few protons, it is not of use for compounds which give complicated splitting patterns of carbon resonances in the proton coupled '3C-NMR spectra.

The technique proposed by Bax2), long range J C-H resolved 2D spectroscopy (LRJR), has overcome this problem and enables to observe selectively only long range couplings between carbons and a given proton. This method is based on an existing 2D-Fourier transform experiment3) which detects 13C spin echoes modulated by heteronuclear spin-spin coupling, but it uses a frequency-selective 180° radiofrequency pulse applied to an isolated proton resonance. In our experiments, however, we used selective