ABSTRACT
Experimental .......................................................................................................... 190 General Methods ............................................................................................... 190 Methyl 4,6-O-benzylidene-α-d-glucopyranoside (2)........................................ 191 Ethyl 4,6-O-benzylidene-1-thio-β-d-glucopyranoside (4) ................................ 191 Ethyl 4,6-O-benzylidene-1-thio-β-d-galactopyranoside (6) ............................. 192
Acknowledgments .................................................................................................. 192 References .............................................................................................................. 196
Benzylidene acetals have found broad application in synthetic carbohydrate chemistry. A new chiral center (PhC*H<) is formed during their formation, wherein the bulky phenyl substituent adopts predominantly the thermodynamically more stable equatorial orientation. Our laboratory has previously developed a simple protocol for the preparation of methyl 4,6-O-benzylidene-α-d-glucopyranoside (2) from commercially available methyl α-d-glucopyranoside (1). The purication of the product was achieved by simple precipitation without the need for chromatographic separation.1 Herein, we describe the application of this procedure to the synthesis of benzylidene acetals of ethyl thioglycosides 3 and 5. All product purication can be achieved by crystallization/precipitation only. Additional quantities and hence higher yields can be achieved by subsequent chromatography of the mother liquor.
