Unexpected formation of a d-chiro inositol from a l-chiro precursor

In a one-step procedure, l-1-O-benzyl-2-O-methyl-chiro-inositol (1) was acetalized to the l-muco-inositol derivatives 2, 3 and d-2-O-benzyl-3-O-cyclohexylcarbamoyl-4-(N,N′-dicyclohexylureido)-4-deoxy-1-O-methyl-5,6-O-trichloroethylidene-chiro-inositol (4). l-1-O-Benzyl-6-O-cyclohexylcarbamoyl-3-O-formyl-2-O-methyl-4,5-O-trichloroethylidene-muco-inositol (3) was quantitatively deformylated to l-1-O-benzyl-6-O-cyclohexylcarbamoyl-2-O-methyl-4,5-O-trichloroethylidene-muco-inositol (2) by boiling methanolic triethylamine.