Complete assignment of the ¹H and ¹³C NMR spectra of 8‐hydroxy‐7‐methoxy‐4‐methyl‐1α,4α,4aα,8β,8aα‐tetrahydro‐1,4‐methanonaphthalen‐5(1H)‐one

Abstract

DielsAlder cycloaddition of a mixture of l-aod 2-methylcyclopentadienes ( l a and lb, respectively) to 2-methoxyp-benzoquinone (2) gave a mixture of isomeric endo [ 4 + 21 cycloadducts (3a-3d). Fractional recrystallization of this product mixture from EtOAc-hexane gave ó-rnethoxy-l-methyl-la,4a,4aa,8aa-tetrahydro-1,4 methanonaphthalene-5,8-dione (3a). Reaction of 3a with NaBH, in the presence of cerium(I1I) chloride resulted in the selective reduction of the l e s hindered C=O group in 3a, thereby affording 8-hydroxy-7-methoxy-4methyl-1a,4a,4aa,8~,8aa-tetrahydro-1,4-methanonaphthalen-~lH)-one (4). The 'H and "C NMR spectra of 4, a novel tricyclic ketoalcohol, have been completely assigned by using a combination of one-and two-dimensional NMR techniques. KEY WORDS 'H and I3C NMR chemical shift assignments Tricyciic ketoalcohol COSY RELAYHLong-range HETCOR

Complete assignment of the 1H and 13C NMR spectra of four 2‐substituted 4a,8a‐cis‐endo‐5,8‐methano‐4a,5,8,8a‐tetrahydronaphthalene‐1,4‐diones

“…In connection with literature data on the 1 H NMR spectra of enediones 1 and 2 and related compounds, it must be pointed out that, regrettably, there is no consensus regarding the labeling of the protons attached to C-9: the one we use, with H-9s facing the norbornenic double bond, is also favoured by Minter et al 1 but Yates and Switlak 11 prefer to label syn and anti in the opposite sense. The assignment of most of the signals in the corresponding 13 C NMR spectra was obtained with the help of HETCOR experiments, while 13 C NMR spectra acquired with proton gated decoupling (GATEDEC) were used to ascribe the signals due to each of the carbonyl carbons, because C-1 is coupled to H-8a, whereas C-4 has couplings to H-4a and H-3 ( Table 4).…”

“…1 Among them, the enediones, besides being of interest in themselves as analogues of the anti-HIV compound conocurvone, 2 are particularly valuable as intermediates in the synthesis of substituted benzoquinones, 3 -5 some of which are antimetabolites 6,7 of coenzyme Q, exhibiting antitumoral, 6 antimalarial 6 and/or Leishmanicidal 8 activities, while other quinones have attracted renewed technological interest for the chromium-free (in fact, allmetal-free) tanning 9,10 of leather.…”

Assignment of the 1H and 13C NMR spectra of 1-methyl-6-phenyl-1α,4α,4aα,5α,8β,8aα-hexahydro-1,4-methanonaphthalene-5,8-diol

“…[1][2][3] Pursuant to our continuing interests in the synthesis and chemistry of novel polycarbocyclic "cage" compounds, 4 several substituted 1,4-methanonaphthalenes have been prepared. 5 In addition, we have reported the results of detailed NMR studies of several compounds of this general type.…”