A-Keto-/-lactones

SL 358 (1995) (a-keto lactone and amide, a-amino ketone hydrochloride)... 

The same catalyst effects asymmetric reduction of a-keto lactones (equation I)2 and -kelo carboxylates.3... 

The present method has been successfully applied10 to the asymmetric reduction of various a-keto carboxylates and a-keto lactones. 

OL-Keto lactones. Lactones can be converted into a-keto lactones by conversion to an enamino lactone by reaction with tris(dimethylamino)methane followed by photooxidation in CH2CI2 at - 78°. The a -keto lactones exist mainly or exclusively in the enol form and do not undergo normal Wittig condensation. 

Beginning with 3-oxycyclopentane methylcarboxylate some natural products have also been synthesized. The key intermediate for the preparation of dihydro-jasmone240), cis-jasmone240), (Eq. 123) and sarkomycin241) (Eq. 124) is a keto-lactone, which is obtained from 3-oxo-cyclopentane methylcarboxylate (Eq. 122) 239a>... 

Scheme 13) under similar conditions to those discussed earlier (cf. Scheme 11) to liberate a-amino lactone 75, subsequent transamination using the methiodide of pyridine-4-carboxaldehyde, DBU, and DMF in CH2CI2 served to unveil a-keto lactone 24 in 70% yield, presumably through the defined mechanism. With this critical motif in place, all that now remained was to incorporate... 

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