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See, for example, K. Wuthrich and R. Baumann. Org. Magn. Reson., 8,532 (1976), and references cited therein. A. Allerhand, D. Doddrell, and R. Komoroski, J. Chem. Phys., 55, 189 (1971). At high magnetic field strengths (such as 63.4 kG), chemical shift anisotropy (CSA) becomes the dominant relaxation mechanism for nonprotonated unsaturated carbons. The CSA mechanism contributes slightly ( 5 10 % at 63.4 kG) to 1/ T1 of hydrogen-bearing unsaturated carbons. However, CSA relaxation makes a totally negligible contribution to the relaxation of hydrogen-bearing saturated carbons (such as N carbons of a protein) at all magnetic field strengths available today for high resolution NMR. For details, see R. S. . For any given choice of rCH, each measured T1 value actually yields two solutions for r R (see Figure 1). However, we have rejected one solution in each case (2.9 ns at 14.2 kG and 0.19 ns at 63.4 kG). because these solutions correspond to NOE values (see Figure 1) which are much higher than measured ones.

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[lihydrotolunldeh~des 5 and li and their aromatization products 7 arc isolated. 1 t is concluded t h a t these products arise froin 2-, 3 -and 7-1iictliyl-hcpta-Z,4,6-tric1ial 2 a, 2 b m t l 2f which arc louinctl from 1 ajlb lip patlh C ant1 11 in Scheme 2 involving it formal [ 2 i~(iI-c!.cloreversion rcaclion of lajl b and of its \-alencc isomer, 1,2-homooxepiiic 11. Two altci-natc pathways, -1 and I;, in\-olving cleavage o f thc. (', C bond common to 1)oth rings in 1 conc~riiiitant or followed b>-li!~tlrr)~cii shifts i m ' not opcmtivc.Einleitung. -I(urz1i:h habcn wir gezeigt, dass 8-Oxa-bii 5 t 101 5 1 0 Iocta-2,khen (1, I< = H) beim Er1iitzi.n in Losung oder in der Gasplia5e eine King5paltung zum Hepta-2,4,6-trienal (2, X = H) erleidet, welcliei uber cine nur indirekt nachweisbare Ketenzn isclienstufe rnit Ricyclor3.2.01hept-2-en-7-on (3, I< = H) im Gleichgewicht steht, und bei holierer Tl:mperatur vom Aldehyd 4 (I< = H) 'I( 11 ableitende, stabile