Preparation and Taste of Certain Glycosides of Flavanones and of Dihydrochalcones

The 7-O-[2-O-(alpha-L-Rhamnopyranosyl)-beta-L-quinovoside] of naringenin and of hesperetin, and their dihydrochalcone (DHC) derivatives were synthesized by the method of Koenigs-Knorr (Ag2CO3 and quinoline). The reaction of TMS ethers of naringenin and of hesperetin with each of the alpha-acetofluoro derivatives of D-glucose, L-rhamnose, 2-O-(alpha-L-rhamnopyranosyl)-L-rhamnose, and 2-O-(alpha-L-rhamnopyranosyl)-D-glucose (neohesperidose), using boron trifluoride etherate as an activator, yielded coupling products which, after deprotection, gave naringenin 4'-O-beta-D-glucoside, naringenin 4'-O-alpha-L-rhamnoside, naringenin 4'-O-[2-O-(alpha-L-rhamnopyranosyl)-alpha-L-rhamnoside], hesperetin 3'-O-[2-O-(alpha-L-rhamnopyranosyl)-alpha-L-rhamnoside], and naringenin 4'-O-beta-neohesperidoside, respectively. Catalytic hydrogenation of these flavanones gave the corresponding DHC derivatives. Hesperetin DHC 4'-O-[2-O-(alpha-L-rhamnopyranosyl-beta-L-quinovoside] was 300 times sweeter than sucrose, while the other compounds were bitter or tasteless.