Optically active (4S,αR)- and (4R,αR)-4-hydroxymethyl-3-(α-methylbenzyl)-2-oxazolidinones (2 and 3, respectively) were synthesized from 2-(α-methylbenzyl)amino-1,3-propanediol (1) using CDI and Et3N or DBU in CH2Cl2 or THF at room temperature in 17–87% yields and in 4–90% de. The intermediates of the reaction were a diastereomixture of monoimidazolylcarbonyl compounds 4/5 (67:33), and (R)-5-(α-methyl)benzylamino-1,3-dioxan-2-one (6) was also formed as a precursor of 2/3 from 4/5. Cyclic carbonate 6 were converted into 2 in >96% yields and in 94–92% de by treatment of DBU in CDCl3 and THF-d8 at room temperature; however, little amount of 2 was formed from 6 by treatment of Et3N in CD2Cl2. Thus, the yields and diastereoselectivities of the reaction using CDI form 1 to 2/3 depended on the ratios of the reaction paths from 4/5 directly to 2/3 or from 4/5 to 2/3 via 6.
