Reducing Ketones with Carrots

Significance

The carrot-mediated keto reduction of cyclic 3-oxoamines is reported. The straightforward synthetic procedure utilizing daucus carota slices in its unmodified form in aqueous media ­delivered the products in high yields and enantio-selectivities. The mechanism of this biochemical transformation presumably proceeds via a pro-(R) hydride transfer from the NADH present in the plant cells, which is in accordance with a Prelog model previously discussed in the literature ­(Glasfeld and co-workers Proc. Natl. Acad. Sci. USA 1991, 88, 8420). The reduction of cyclic oxo-amines derived from proline led to products with opposite configuration on the newly formed stereocenter.