Uses
2-Methoxyethoxymethyl chloride, is used as selectively cleaved under aprotic conditions in the presence of a wide range of OH-protected reagents. It is used as an OH-protecting reagent. An examples of the target molecule MEM Chloride is the side chain of roxithromycin. It is also used in the protection of the OH groups in serine and threonine during peptide synthesis. Some of the other applications include have the ability to coordinate to metals, which is thought to accelerate the cleavage by Lewis acids. The chelating ability of the MEM ether also makes it useful as a stereodirecting group in organometallic reactions, first noted in the stereo controlled addition of ?-methoxyvinyllithium to a carbonyl in the synthesis of taxusin.
Purification Methods
Possible impurities are methoxyethanol (b 124o/atm), HCHO and HCl which can be removed below the boiling point of MEMCl. Purify MEMCl by fractional distillation in a vacuum. If too impure, prepare it from methoxyethanol (152g) and s-trioxane (66g) by bubbling a stream of dry HCl (with stirring) until a clear mixture is obtained. Dilute with pentane (900mL), dry (3hours over 100g MgSO4, at 5o), evaporate and the residue is distilled in a vacuum. It is MOISTURE SENSITIVE and TOXIC. The MEM.NEt3+Cl-salt, prepared by reaction with 1.3 equivalents of Et3N (16hours/25o) and dried in a vacuum, has m 58-61o, and is moisture sensitive. [Corey et al. Tetrahedron Lett 809 1976, Yoshimatsu et al. J Org Chem 59 1011 1994, Greene & Wuts Protective Groups in Organic Synthesis edn, J Wiley & Sons NY 1991.] Carcinogen.
