%0 Journal Article
%T Diastereoselective Spiroannulation of Phenolic Substrates: Advances Towards the Asymmetric Formation of the Manumycin m-C7N Core Skeleton
%A Guy L. Plourde
%A Randy R. Spaetzel
%A Jolene S. Kwasnitza
%A Thomas W. Scully
%J Molecules
%D 2007
%I MDPI AG
%R 10.3390/12092215
%X The asymmetric syntheses of two new spirolactones prepared in optically pure form from L-3-nitrotyrosine are described. The key step, an oxidative spiroannulation, was carried out on the optically active phenols 11a and 11b and afforded the new spirolactones 5a and 5b in 85% and 83% yields, respectively, as mixtures (3:1 dr) of diastereomers. The major diastereomers from these mixtures could be isolated in optically pure form by trituration using acetone-hexanes as the solvent. Thus, the optically active spirolactones (+)-5a (+ 92.8o, c=0.125 acetone) and (+)-5b (+112.0o, c= 0.125 acetone) were obtained after four synthetic steps from L-3-nitrotyrosine in 41% and 43% yield, respectively.
%K Spiroannulation
%K oxidation
%K phenol
%K diastereoselective
%K asymmetric
%K Spiroannulation
%K oxidation
%K phenol
%K diastereoselective
%K asymmetric
%K Spiroannulation
%K oxidation
%K phenol
%K diastereoselective
%K asymmetric
%K Manumycins
%K Aranorosins
%K Gymnastatins.
%U http://www.mdpi.com/1420-3049/12/9/2215