Biphenyl 4-acetyl -4 -methyl

Yet a further increase in potency is observed when the para-isobutyl group is replaced by a benzene ring. One published synthesis for that compound is quite analogous to the malonate route to the parent drug. The acetyl biphenyl (50-1) is thus converted to the corresponding arylacetic acid by reaction with sulfur and morpholine, followed by hydrolysis of the first-obtained thiomorpholide. This is then esterified and converted to malonate anion (50-2) with sodium ethoxide and ethyl formate. The anion is quenched with methyl iodide hydrolysis of the esters followed by decarboxylation yields the NSAID flubiprofen (50-3) [51]. 

The NMR spectra of /V-oxides of biphenyl lactonic alkaloids (O-methyl and O-acetyl derivatives) show the signal of low-field aromatic proton H-24 at 5 8.1 -8.7 ppm. The Dreiding models indicate that this proton is deshielded by the N—O group. H-24 resonates in the cis-fused derivatives at 0.13-0.28 ppm lower field than in the corresponding trans forms (24). The same relation is observed in the NMR spectra of biphenyl ether alkaloids where H-24 absorbs at 5 7.6-8.2 ppm (25, 36). 

CO, CHi. CO2, ethylene, acetylene, ethane. H2O. propylene, ethanal acetone, propanal, ethanol, benzene, toluene, ethylbenzene, styrene, p-vinyltoluene, benzaldehyde, p-ethyl-totuene acetophenone, methyl benzoate, vinyl benzoate, ethyl benzoate, p-methyl-acetophenone. benzoic acid, p-methyl vinyl benzoate, p-vinylacetophenone, propyl benzoate, p-ethyl vinyl benzoate, p-vinyl vinyl benzoate, biphenyl. 1-hydroxyethyl benzoate, diacetylbenzene. p-acetyl vinyl benzoate, divinyl terephthalate. ethyl vinyl terephthalate. ethyl vinyl terephthalate, p-acetyibenzoic acid, methyl 1-hydroxyethyl terephthalate. ethylene dibenzoate... 

The synthesis of the lichen dibenzofuran pannaric acid (470) from pannarol (471) was reported by Elix 110) (Scheme 59). Pannarol has been synthesized via a mixed Ullmann reaction and subsequent hydrobromic acid induced cyclisation of the unsymmetrical biphenyl separated from the mixture of three products (2). Pannarol (471) was methylated and then acetylated to yield a mixture of 2,6-diacetyl-3,9-dimethoxy-l,7-dimethyl-dibenzofuran (472) and 4,6-diacetyl-3,9-dimethoxy-l,7-dimethyldibenzo-furan (473), which were separated by preparative t.l.c. The major product (472) was then oxidized and demethylated to yield pannaric acid (470). 

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