PREPARATION AND TASTE OF CERTAIN GLYCOSIDES OF FLAVANONES AND OF DIHYDROCHALCONES

The [2-O-(alpha-L-Rhamnopyranosyl)-beta-L-quinovoside] of naringenin a nd of hesperetin, and their dihydrochalcone (DHC) derivatives were syn thesized by the method of Koenigs-Knorr (Ag,CO, and quinoline). The re action of TMS ethers of naringenin and of hesperetin with each of the alpha-acetofluoro derivatives of D-glucose, L-rhamnose, 2-O-(alpha-L-r hamnopyranosyl)-L-rhamnose, and 2-O-(alpha-L-rhamnopyranosyl)-D-glucos e (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 2-O -(alpha-L-rhamnopyranosyl)-alpha-L-rhamnoside], hesperetin 2-O-(alpha- L-rhamnopyranosyl)-alpha-L-rhamnoside], and naringenin 4'-O-beta-neohe speridoside, respectively. Catalytic hydrogenation of these flavanones gave the corresponding DHC derivatives. Hesperetin DHC -[2-O-(alpha-L -rhamnopyranosyl-beta-L-quinovoside] was 300 times sweeter than sucros e, while the other compounds were bitter or tasteless.