Microfluidic a-Sialylation

FIGURE 8.1 Continuous flow synthesis using microreactor and affinity separation system. Ac, acetyl Bn, benzyl TfO, triflate Troc, trichloroethoxycarbonyl. 

An efficient a-sialylation that took advantage of the highly reactive sialyl donors having C5 cyclic imides, especially phthalimide (NPhth), by virtue of the fixed-dipole moment effects, was also reported [42], For example, the use of the sialyl donor 4 and acceptor 6 at -78°C supplied the sialoside 7 as a only with 92% yield on 50 mg scale. The scale-up in batch process, however, significantly decreased the yield and stereoselectivity. This decrease in sialylation efficiency might be a result of 

TABLE 8.1 Microfluidic Sialylation Using /V-Phthaloyl- and Azido-Protected Donors  

Entry Donor Donor Cone. (M) TMSOTf Cone. (M) Yield a/p 

Conditions (a) TMSOTf, CH2C12 (b) Et3N (c) PPh3, DDQ (d) TMSOTf, CH2Cl2/C4F9OEt (1/1) 

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Examination of the same mannosylation was performed by using the integrated microfluidic and batch systems as described earlier for microfluidic a-sialylation by the N-acetylated imidate 15 [19]. The Comet X-01 micromixer utilized for this case has a channel width of 500 pm (Fig. 8.5) because the micromixing with IMM mixer... 

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