
%0 Journal Article
%A Baker, Robert W. 
%A Kyasnoor, Rekha V. 
%A Sargent, Melvyn V. 
%A Skelton, Brian W. 
%A White, Allan H. 
%T Formal Synthesis of Both Atropomers of Desertorin C and an Example of Chirality Transfer from a Biphenyl Axis to a Spiro Centre and its Reverse
%J Australian Journal of Chemistry
%D 2000/09/01
%V 53
%N 6
%P 487-506
%K Asymmetric synthesis; atropomers; chirality transfer; desertorin C.
%R https://doi.org/10.1071/CH99134
%U https://www.publish.csiro.au/paper/CH99134 
%X In connection with the synthesis of 4,4&#8242;,7,7&#8242;-tetramethoxy-5,5&#8242;-dimethyl-6,8&#8242;-bicoumarin (desertorin C) (11) in enantiopure form, the diastereomeric ratios of the products of the reactions between 2-isopropyloxy-6-methoxy-4- methylphenylmagnesium bromide (24) and (4S)-4-isopropyl-2-(2,3,5-trimethoxyphenyl)-4,5-dihydrooxazole (23), between 2,4-dimethoxy-6-methylphenylmagnesium bromide (37) and (4S)-4-isopropyl-2-(2,3-dimethoxy-5-methylphenyl)-4,5-dihydrooxazole (36), and between 2,4-dimethoxy-6-(t-butyldimethylsilyloxy)methyl-phenylmagnesium bromide (46) and the oxazole (36) were explored. The major product of the last mentioned reaction was converted into (S,4S)-4-isopropyl-2-(2&#8242;-hydroxymethyl-4&#8242;,6,6&#8242;-trimethoxy-4-methyl-1,1&#8242;-biphenyl-6-yl)-4,5-dihydroxazole (49), the axial configuration of which was confirmed by single crystal X-ray structural determination. The similar product (S,4S)-2-(2&#8242;,4&#8242;,6-trimethoxy-4,6&#8242;-dimethyl-1,1&#8242;-biphenyl-6-yl)-4,5-dihydrooxazole (43) was converted into (S)-1-(2,4&#8242;,6&#8242;-trimethoxy-4,6&#8242;-biphenyl-2-yl)ethanone (57) which furnished (S)-1-(2&#8242;,4&#8242;,6-trimethoxy-4,6&#8242;-dimethyl-1,1&#8242;-biphenyl-2-yl)acetamide (58) (43%) and (S)-2,7&#8242;-dimethoxy-3&#8242;,5&#8242;,6-trimethylspiro&#91;cyclohexa-2,5-diene-1,1&#8242;-(1H)isoindole&#93;-4-one (61) (30%) on Schmidt rearrangement. The dienone (61) on reduction and methylation regenerated the ketone (57). The methodology of Lipschutz was adapted for the synthesis of both enantiomers of 1,1&#8242;-(2&#8242;,4-dihydroxy-6,6&#8242;-dimethoxy-2,4&#8242;-dimethylbiphenyl-3,3&#8242;-diyl)bisethanone (32) and (83) which constitutes a formal synthesis of both enantiomers of desertorin C. 
