264
2
General Synthetic Methods
⊡ Scheme 79
Lithium diphenylphosphine (LiPR 2 ) has also been used to substitute sulfonates on sugar derivatives such as 183 and 185 to yield, after spontaneous oxidation, 184 and 186
( > Scheme 79) [124].
5.2 Ring-Opening Reactions
Epoxide ring opening is also an alternative route for the introduction of a phosphorus atom into
carbohydrates. Thus, the D-allo epoxide 72 reacts with LiPPh 2 , giving an intermediate phosphine which is spontaneously oxidized to the 2-phosphonate 187 [125], whereas the isomeric
D-manno epoxide 188 affords the regioisomeric 3-phosphonate 189 ( > Scheme 80) [124].
⊡ Scheme 80
A slight excess of potassium diphenylphosphine can open the oxetane ring of compound 190
to afford phosphine 191 ( > Scheme 81) [126].
2
General Synthetic Methods
⊡ Scheme 79
Lithium diphenylphosphine (LiPR 2 ) has also been used to substitute sulfonates on sugar derivatives such as 183 and 185 to yield, after spontaneous oxidation, 184 and 186
( > Scheme 79) [124].
5.2 Ring-Opening Reactions
Epoxide ring opening is also an alternative route for the introduction of a phosphorus atom into
carbohydrates. Thus, the D-allo epoxide 72 reacts with LiPPh 2 , giving an intermediate phosphine which is spontaneously oxidized to the 2-phosphonate 187 [125], whereas the isomeric
D-manno epoxide 188 affords the regioisomeric 3-phosphonate 189 ( > Scheme 80) [124].
⊡ Scheme 80
A slight excess of potassium diphenylphosphine can open the oxetane ring of compound 190
to afford phosphine 191 ( > Scheme 81) [126].