Synthesis of 2-Substituted (±)-(2R,3R,5R)-Tetrahydrofuran-3,5-dicarboxylic Acid Derivatives†
journal contributionposted on 16.02.2001, 00:00 by Gary T. Wang, Sheldon Wang, Yuanwei Chen, Robert Gentles, Thomas Sowin
An efficient synthesis of 2-substituted (±)-(2R,3R,5R)-tetrahydrofuran-3,5-dicarboxylic acid derivatives has been developed. Starting from 5-norborne-2-ol, the key intermediate (±)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) was synthesized in an efficient six-step sequence. The key transformation is the base-catalyzed methanolysis−rearrangement of (±)-6,7-exo,exo-(isopropylidenedioxy)-4-exo-iodo-2-oxabicyclo[3.2.1]octan-3-one (14). Further manipulation of the 3-substituent of (±)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) followed by deprotection of the diol moiety and ring opening catalyzed by RuCl3/NaIO4 gave the title compounds in good yield.