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8.4.3.2.3 Variation 3: Substitution Using Cesium Carboxylates Activated by Crown Ethers

DOI: 10.1055/sos-SD-008-01308

Kellogg, R. M.Science of Synthesis, (200681509.

Dimethylformamide, which has been used in reactions described in the preceding sections, is rather high-boiling, and this can provide experimental problems, especially with temperature-sensitive products. Alternative procedures have been developed in which benzene or toluene is used as solvent, and 18-crown-6 is used to solubilize and activate the cesium (and, in some cases, potassium) carboxylates.[‌54‌] This methodology may be applied in the conversion of the protected and activated β-D-galactopyranoside 39 into the protected β-D-mannopyranoside 41 via 40 (Scheme 15).[‌55‌] Other, related conversions are known.[‌56‌‌58‌]

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Meeeeeeeeeee Meeeeeeeee

Meeeee 8,8-Me-M-eeeeee-8,8-ee-M-eeeeeeee-β-M-eeeeeeeeeeeeeee (88):[‌88‌]

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(88α)-8-Meeeeeeeee-8-ee-88-ee Meeeeee (88α-Meeeeeeeeeee Meeeeee; 88):[‌88‌]

Meeeeeeeeeee eee eeeeeeeee eeee eee eeeeeeeeeeeeeeeeeeeeee eeeeeeeeee 88 ee eeeeeeeee eeee MeMM8MM8Me ee eeeeeeee. M eeee ee eee eeeee eeeeeeeeeeeeeeeeeeeeee 88 (eeeeeeee eee eeeeeeeeeeeee eee eeeeeeee), MeMMe (8.8 eeeee), eee 88-eeeee-8 (8.8 eeeee) ee eeeeeee (MMMMMMM: eeeeeeeeee) eee eeeeeeee eee 88e. Meeeee eeeeeeee 88α-eeeeeeeeeeee eeeeeee (88) eeeeeeee eeee eeeeeeeeeeee eeeeee(e) (88%); eeeee: 88%. [88α-Meeeeeeeeeee eeeeeee (88) eee eeeeeeeeee ee eeeeeeeeee ee 88α-eeeeeeeeeeee, eeeee eee eeeeeeee eeee ee eeeeeeeee eeeeee.]

(8M,8M,8M)-8-Meeeeeeee-8-eeeeeeeeeeeeeeee Meeeeeee (Meeeeeeeee Meeeeeee; 88):[‌88‌]

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References


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