Electrochemical oxidation of (R)-4-hydroxy-2-pyrrolidone: A key building block for stereoselective N-acyliminium ion coupling reactions

The 5-methoxylation of (R)-4-hydroxy-2-pyrrolidone can be performed success fully by direct electrochemical oxidation at 40 mA/cm(2) in methanol at gra phite electrodes using an undivided cell and sodium benzene sulfonate as su pporting electrolyte. After direct protection of the intermediate as TBDMS ether, (4R)-4-tert-butyldimethylsilyloxy-5-methoxy-2-pyrrolidone 3 can be u sed in various diastereoselective amidoalkylation reactions. In most cases cis-stereoselectivity is observed. However, the favored cis-addition may be typical only for Si-organic compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.