Diastereo-switching method

We have developed two methods for the synthesis of natural and unnatural products from D-glucose. Enantio-and diastereo-switching method established a new strategy for the synthesis of four possible stereomers for natural products synthesis, and this powerful method was successfully applied to the synthesis of unnatural protein phosphatase inhibitors. The second synthetic method involved the preparation of the urea-glycosidic linkages for the synthesis of glycopeptide mimics. 

Enantio-switching and Diastereo-switching Method for Natural Products... 

Initial investigations showed that the treatment of trimethylsilyl nitronate 23a (R1 = Me) with benzaldehyde (R2 = Ph) in the presence of (S,S)-6b (X = HF2, 2 mol %) in TH F at —98 °C for 1 h and at —78 °C for 1 h and subsequent hydrolysis with 1M HC1 at 0 °C, resulted in clean formation of the corresponding nitroalkanol 24 (R1 = Me, R2 = Ph) in 83% yield (anti/syn = 74 26) with 33% ee (anti isomer) (entry 1 in Table 9.5). Notably, the poor diastereo- and enantioselectivities were dramatically improved by switching the catalyst to (S,S)-6c (X = HF2) possessing a radially extended 3,3-aromatic substituent (Ar), and 24 (R1 = Me, R2 = Ph) was obtained in 92% yield (anti/syn = 92 8 with 95% ee (anti isomer) (Table 9.5, entry 2). This asymmetric nitroaldol protocol tolerates various aromatic aldehydes to afford anti-nitroaldols selectively, being complementary to Shibasaki s method... 

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