The enantioselective additionof diethylxinc to ztldehydes using 1,2-isopropylidene-Sdeoxy-5-dialkylammO-U-D-XylOfuranOse8 derived from a-D-xylose as new catalysts provided the corresponding alcohlos with 75-96 % ee.
Enantioselective addition of diethylzinc to aldehydes by chiral ligands is a convenient method for the preparation of optically active secondary alcohols.' Accordingly. a wide variety of chiral catalyS8 for the enantioselective addition reaction has been extensively developed."
Among them, most of highly effective chiral cataly8ts for the reaction am p-aminoakohol8 derived fmm natural products, such a8 camphor, a-amino acids, norephedrine and cinchona alkaloids. And also several kind8 of unnatural chiral aminoalcohol derivatives proved to be potentially chiral catalysts to afford high optical induction for such reaction.
However, no report using chiral catalysts derived from carbohydrates in this reaction ha8 not appeared in literatures, although carbohydrates am widely used chiral auxiliaries for asymmetric syntheses.2 We wish hereby to report the enantioselective addition reaction of diethylxinc to aldehydes using yaminOatcOhol8, 1Zisopropylidene-5-deoxy-5-dialkylamino-a-D-xylofurano8es l-3 as new chiral catalysts, which were prepared from I.2-isopropylidene-5-O-p-toluene8ulphonyl-a-D-xylo~o~3 and the corresponding amine8.4 First, we compared the asymmetric inductions of the chiral catalysts for benzadehyde 4a chosen as a representative aldehyde. Thus, 4a was reacted with diethyizinc in the presence of 5 mole 45 of each of l-3 in toluene at room temperature (m. 25 "C). The maction with the exception of 2 pm smoothly to afford I-phenylptopanol Sa in high yields. The addition reaction with 2 was very slow at room temperature ( 20 % yield, 24 h), but was complete in 2 h at 70 "C. The optical yield8 of product alcohol 5a obtained am 87 % ee with 1, 78 % ee with 2 and 96 % ee with 3. The results led us to investigate the catalytic enantioselective