Chiral hetero Diels-Alder products by enantioselective and diastereoselective zirconium catalysis. Scope, limitation, mechanism, and application to the concise synthesis of (+)-Prelactone C and (+)-9-deoxygoniopypyrone.
Catalytic asymmetric hetero Diels-Alder (HDA) reactions using a chiral zirconium complex have been developed. The reactions of aldehydes with Danishefsky's dienes proceeded smoothly to afford the corresponding pyranone derivatives in high yields with high diastereo- and enantioselectivities in the presence of a chiral zirconium complex, which was prepared from zirconium tert-butoxide, (R)-3,3'-diiodobinaphthol or its derivative, a primary alcohol, and a small amount of water. It is noted that 2,3-trans-pyranone derivatives were obtained with remarkably high diastereo- and enantioselectivities in the reaction with 4-methyl Danishefsky's diene. This is the first example of catalytic asymmetric trans-selective hetero Diels-Alder reactions of aldehydes. Furthermore, asymmetric HDA reactions with 4-benzyloxy Danishefsky's dienes were conducted to afford 2,3-cis-pyranone derivatives in high selectivities. Isolation of an intermediate of this asymmetric hetero Diels-Alder reaction indicated that the reaction proceeded in a stepwise cycloaddition pathway. Finally, these catalytic, asymmetric hetero Diels-Alder reactions were successfully applied to concise syntheses of biologically important natural pyranone derivatives, (+)-Prelactone C and (+)-9-deoxygoniopypyrone.
Yamashita
Yasuhiro
Y
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Japan.
Saito
Susumu
S
Ishitani
Haruro
H
Kobayashi
Shū
S
D000447:Aldehydes / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D002384:Catalysis; D007783:Lactones / Q000138:chemical synthesis*; D011714:Pyrans / Q000138:chemical synthesis; D013237:Stereoisomerism; D015040:Zirconium / Q000737:chemistry*
D000447:Aldehydes; D000475:Alkenes; D007783:Lactones; D011714:Pyrans; C474101:prelactone C; C073078:9-deoxygoniopypyrone; D015040:Zirconium