Synthesis of ribo-hexopyranoside- and altrose-based azacrown ethers and their application in an asymmetric Michael addition

The synthesis of four new ribo-hexopyranoside-based chiral lariat ethers of monoaza-15-crown-5 type and two altropyranoside-based crown ethers were elaborated. Our syntheses utilized the regioselective ring opening of the oxiran moiety of the 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. The reaction of methyl-2,3-anhydro-4,6-O-benzylidene-α-d-mannopyranoside with ethanolamine is especially of interest to afford a 3-substituted altropyranoside. One of the ribo-hexopyranoside-based lariat ethers with a 4-methoxyphenyl substituent induced an enantioselectivity of 80% when used as catalyst in the Michael addition of diethyl acetamidomalonate to trans-β-nitrostyrene under phase transfer catalytic conditions.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We synthesised ribo- and altropyranoside-based crown ethers by new methods. ► Regioselective ring openings of the oxiran moiety of the 2,3-anhydro sugars. ► Selective protection of primary hydroxyl group by Mitsunobu reaction. ► One of the lariat ethers that induced an enantioselectivity of 80% used as catalyst.