Starting-materials for Preparing Trimethyl Derivatives

Selective trimethylation at positions 2, 3 and 4 is obtainable by the use of (a) the 6-trityl derivatives of the methyl a- and /S-2 D-galacto-pyranosides or 6-trityl-D-galactopyranose3 itself, (f ) the 1,6-anhydro-/S-D-galactopyranose,4 M (c) the methyl /9-D-galactopyranoside 6-nitrate,7 and id) the methyl 6-tosyl-a-D-galactopyranoside.M 

Selective trimethylation at positions 3, 4 and 6 has been accomplished by starting with the 1,2-isopropylidene-D-galactopyranose.10 The methyl 2-tosyl-/9-D-galactopyranosideu could also be used although no instance has so far been recorded. 

Selective trimethylation at positions 2, 3 and 6 has not been accomplished because no suitable starting material is known having free hydroxyls at these three positions and having those at 4 and 5 masked. 

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