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Zemplen deacylation

The preparation of 3,5-bis(/3-D-glycopyranosyl)-l,2,4-thiadiazoles has been accomplished via the oxidation of the corresponding acylated C-(/3-D-glycopyranosyl)thioformamides with potassium and sodium dithionite. The synthesis is completed by a Zemplen deacylation. This is an interesting extension to a type A synthesis which has previously only been suitable for arylthioamides <2001T5429>. [Pg.503]

Zemplen deacylation is the most commonly used deblocking reaction for the removal of ester protecting groups [220]. Using this transesterification reaction, OH-functions can be regenerated under mild conditions, in methanol with a catalytic amount of sodium methoxide at room temperature. The difference in the rate of benzoate and acetate solvolysis is sufficient to enable removal of acetates in the presence of benzoates. Typical conditions for this selective cleavage include ammonia in MeOH. [Pg.131]

The 3a-tropanol 0-riboside (23) has been prepared by trans-glycosylation of the amino-alcohol with l-0-acetyl-2,3,5-tribenzoyl-ribofuranose, catalysed by boron fluoride etherate, followed by Zemplen deacylation in methanol, with sodium methoxide as a catalyst. [Pg.61]

Preparations of various spiro-ketals have been reported photolysis in the presence of diacetoxyiodobenzene and iodine converted co-hydroxyalkyl C-glyco-sides into [6.5]-, [5.5]-, [5.4]-, and [4.4]-ring systems (e.g.. 43 -> 44). " Intramolecular Friedle-Craft reaction of 6-0-acetyl-3,4-di-C>-benzoyl-2-C>-benzyl-a-D-glucopyranosyl chloride, followed by oxidation of the benzylic methylene group of the cyclic ether moiety and Zemplen deacylation gave lactone 45, which in aqueous solution exists mainly as the hydroxy acid 46. ... [Pg.8]


See other pages where Zemplen deacylation is mentioned: [Pg.144]    [Pg.301]    [Pg.59]    [Pg.522]    [Pg.155]    [Pg.233]    [Pg.144]    [Pg.301]    [Pg.59]    [Pg.522]    [Pg.155]    [Pg.233]    [Pg.82]   
See also in sourсe #XX -- [ Pg.131 ]




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