Permethylation Hakomori procedure

In 1984, a procedure for permethylation of carbohydrates using iodomethane, catalyzed by sodium hydroxide139 was introduced that was shown to result in higher yields of permethylated products in a shorter reaction time than the Hakomori permethylation. It is this method of permethylation that has become routinely used. 

An alternative procedure for the permethylation of polysaccharides is the well-known one described by Hakomori, which employs the methyl-sulfinyl carbanion in methyl sulfoxide and methyl iodide. This newer approach was based on the observation that conversion of phenols into phenoxides is greatly enhanced by virtue of the high basicity of this car-... 

The Hakomori method has also been used extensively in the methylation of carbohydrates however, yields were typically low and non-sugar products were observed. Subsequent studies by Ciucanu and Kerek [40] led to the conclusion that OH and H were more effective bases than the methylsulfinyl carbanion. These authors developed a new method for the permethylation of carbohydrates using CH3I and solid NaOH in DMSO. This reaction is relatively clean, proceeds to completion in about 6-7 min, and gives very high yields ( 98%). The derivatization may also be performed with KOH, NaH (excess) and sodium t-butoxide. Ciucanu and Kerek have extensively reviewed the experimental parameters and have published a table of procedures, reagents, reaction times and yeilds for various other versions of Ihe permethylation reaction [40]. 

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