Silyl of carbohydrates

TBDMSCl, DMAP, EtjN, DMF, 25°C, 12 h. These conditions were used to silylate selectively a primary over a secondary alcohol. In the silylation of carbohydrates, it was shown that these conditions inhibit silyl migration whereas the use of imidazole as base causes migration." Besides DMAP, other catalysts such as 1,1,3,3-tetramethylguanidine, l,8-diazahicyclo[5.4.0]undec-7-ene (83-99%), l,5-diazabicyclo[4.3.0]non-5-ene, and ethyldiisopropyl-amine have also been used. A chiral guanidine has been used to give modest kinetic resolution of chiral secondary alcohols with TBDMSCl and TIPSCl. ... 

Scheme 7 Selective silylations of carbohydrate derivatives mediated by chiral scaffolding catalysts...

Initially, silylation of carbohydrates and nucleosides was employed as a technique for preparation of samples for gas chromatographic and mass spectral analysis. However, silyl compounds, especially the t rt-butyldi-methylsilyl function ( r -BDMS—), are presently finding use as protecting groups for the hydroxyl function. Bulky functions are preferred as they offer... 

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