One-Pot Stereoselective Synthesis of Furanoid Amino Acids

Significance

Reported is the synthesis of furanoid amino acids through a one-pot Michael addition-aldol reaction sequence. The addition of DMPU after the aldol addition, but before warming to room temperature was essential to achieve the desired cyclization. Only two of the possible dia­stereomers are observed as products. Previous work has shown that this Michael addition proceeds to give almost exclusively anti products (98% de). Therefore, the syn/anti ratio is a result of selectivity within the aldol addition step. Unfortunately, this ratio could not be increased through the use of more sterically demanding aldehydes as this decreased the rate of the aldol addition, thus favoring cyclopropanation to give A.