Heteroatom Exchange
2.3
265
⊡ Scheme 81
The 1,6-anhydro ring of 1,6-anhydro-D-glucopyranose can also be opened by using phosphinic
acid (H 3 PO 2 ) and sodium phosphinate (H 2 PO 2 Na) to give the 6-phosphate derivative [127].
5.3 Addition Reactions
5.3.1 Addition to Carbonyl Compounds
The addition of dialkyl phosphonates [HP(O)(OR) 2 ] to the carbonyl group of oxosugars gives
rise to geminal phosphorus adducts. And the introduction orientation of phosphorus is effected
by steric hindrance on sugar rings.
Thus, for example, the reaction of 1,6-anhydro-2-oxo-carbohydrate 192 with dimethyl
phosphonate gives rise to the 2-phosphonate derivative 193 with a high stereoselectivity
( > Scheme 82) [128]. And the addition of dimethyl phosphonate to the ulose 194 in the presence of DBU affords the (5R)-5-(dimethylphosphinyl)-D-lyso-hexofuranoside derivative 195a
and its (5S)-epimer 195b ( > Scheme 82) [129].
Tosylhydrazones can also undergo additions of pentavalent phosphorus derivatives, such as
alkyl phenylphosphinate [Ph(H)P(O)OR]; dimethyl phosphonate [HP(O)(OMe) 2 ], or dimethyl
phenylphosphonate [PhP(O)(OMe) 2 ], to introduce phosphorus atoms.
For example, compound 196 reacts with dimethyl phenylphosphonate to afford the adduct
197 and reductive removal of the tosylhydrazino group by NaBH 4 leads to the phosphi⊡ Scheme 82
2.3
265
⊡ Scheme 81
The 1,6-anhydro ring of 1,6-anhydro-D-glucopyranose can also be opened by using phosphinic
acid (H 3 PO 2 ) and sodium phosphinate (H 2 PO 2 Na) to give the 6-phosphate derivative [127].
5.3 Addition Reactions
5.3.1 Addition to Carbonyl Compounds
The addition of dialkyl phosphonates [HP(O)(OR) 2 ] to the carbonyl group of oxosugars gives
rise to geminal phosphorus adducts. And the introduction orientation of phosphorus is effected
by steric hindrance on sugar rings.
Thus, for example, the reaction of 1,6-anhydro-2-oxo-carbohydrate 192 with dimethyl
phosphonate gives rise to the 2-phosphonate derivative 193 with a high stereoselectivity
( > Scheme 82) [128]. And the addition of dimethyl phosphonate to the ulose 194 in the presence of DBU affords the (5R)-5-(dimethylphosphinyl)-D-lyso-hexofuranoside derivative 195a
and its (5S)-epimer 195b ( > Scheme 82) [129].
Tosylhydrazones can also undergo additions of pentavalent phosphorus derivatives, such as
alkyl phenylphosphinate [Ph(H)P(O)OR]; dimethyl phosphonate [HP(O)(OMe) 2 ], or dimethyl
phenylphosphonate [PhP(O)(OMe) 2 ], to introduce phosphorus atoms.
For example, compound 196 reacts with dimethyl phenylphosphonate to afford the adduct
197 and reductive removal of the tosylhydrazino group by NaBH 4 leads to the phosphi⊡ Scheme 82