摘要:
The invention provides an efficient process for producing a 2-substituted optically active 2,3-dihydro-4H-pyran-4-one comprising subjecting an aldehyde, which is not bulky and cannot be expected an electronic interaction with a catalyst, such as acetaldehyde, and a Danishefsky diene to a highly enantio-selective asymmetric hetero Diels-Alder reaction in the presence of an asymmetric catalyst readily obtainable from inexpensive starting materials.