Degradations and Rearrangement Reactions
2.7
397
⊡ Scheme 33
⊡ Scheme 34
⊡ Scheme 35
The protected oxyaminoglucoside 151 rearranges to the azafuranose form under deprotecting
conditions [77] ( > Scheme 36).
The mild reaction of the thioureido derivative 153 with methanol produces the compound 154
with migration of the acetyl group. On heating, this compound isomerizes into the cis-fused
cyclic 155 [129] ( > Scheme 37).
Epimerization at C2 of L-gulose 156 on reaction with KCN in buffered aqueous solution is
thought to proceed by way of the open-chain intermediate. Free sugars produce cyclic products
directly on reaction with the Wittig reagent. Thus, 159 is converted into 160 on prolonged
heating with the reagent ( > Scheme 38).
2.7
397
⊡ Scheme 33
⊡ Scheme 34
⊡ Scheme 35
The protected oxyaminoglucoside 151 rearranges to the azafuranose form under deprotecting
conditions [77] ( > Scheme 36).
The mild reaction of the thioureido derivative 153 with methanol produces the compound 154
with migration of the acetyl group. On heating, this compound isomerizes into the cis-fused
cyclic 155 [129] ( > Scheme 37).
Epimerization at C2 of L-gulose 156 on reaction with KCN in buffered aqueous solution is
thought to proceed by way of the open-chain intermediate. Free sugars produce cyclic products
directly on reaction with the Wittig reagent. Thus, 159 is converted into 160 on prolonged
heating with the reagent ( > Scheme 38).