Protecting group improvement by isotopic substitution: synthesis of the quinone system of fredericamycin A

Use of a trideuteriomethyl group for protection of phenolic oxygen (as in 29, Scheme 4), instead of the classical methyl group, serves to suppress an unwanted intramolecular hydrogen transfer (12→14, Scheme 2) during radical cyclization. The resulting spiro compound (31, Scheme 5) can be converted, by selective demethylation and oxidation, into a substance (35, Scheme 6) that represents the spirodiketone-quinone system of the antitumor agent Fredericamycin A.