Iodine → HCID 131720232, compound

Participants

Reaction Conditions

Reaction Steps

Tri-O-acetyl-D-glucal (1.000 g) was dissolved with o-anisic acid (0.671 g, 1.2 equiv.) and iodine (0.186 g, 0.2 equiv.) in 45 mL THF and quickly cooled to -78° C. A 1 mm Hg vacuum line was then attached and the reaction mixture allowed to warm slowly to -5° C. This reaction mixture was allowed to stir for 2 h under these conditions, replacing the lost THF solvent periodically. The reaction mixture was then poured into 50 mL ethyl acetate and washed successively with saturated Na2S2O3, saturated NaHCO3, and brine. The organic layer was then dried over Na2SO4, filtered and the solvent removed under reduced pressure. The resultant crude oil was purified by silica gel chromatography (75% ethyl acetate in hexane) to provide diacetyl-(o-methoxy)benzoyl glucal (1.141 g, 85%) as a mixture of 4 isomers. A 6:1 mixture of the α and β isomers could be separated from a 1.4:1 mixture of 3R and 3S isomers for spectral analysis by silica gel chromatography (20% ethyl acetate). While isomers are produced using this procedure, under the conditions in which the isomeric mixture is subsequently added to the 7-hydroxymethylcamptothecin (see below), a single intermediate is formed resulting in a single final stereochemical product.

Provenance & Evidence