Sugar cuprate

In 1991, new syntheses of C-disaccharides incorporated Lewis acid mediated couplings with allylsilanes. Additionally, alkyllithium sugar derivatives were coupled to sugar lactones and electron deficient anions were added to sugar carbonates. Finally, complimentary to the anion chemistry used, sugar cuprates were utilized. 

The photochemically induced radical addition of alcohols to enones has been described by Fraser-Reid [104-109]. Here again, the sense of addition depends on the steric effects of substituents, attack anti to the C-5 substituent being preferred [108,110]. Other uses of sugar-derived enones to trap radicals have been reported [111]. Enolone 77 gave interesting results in terms of selectivity [112]. In this instance, radical addition occurs with an equatorial selectivity, whereas cuprate addition occurs with an axial selectivity [9,62]. 

D. R. Hicks, R. Ambrose, and B. Fraser-Reid, Lithium dimethyl cuprate cleavage of diastereomeric 2,3-anhydro sugars a route to 2- and 3-C-methyl hex-2-enopyranosides,... 

Cuprates have also been shown to be effective nucleophiles. Cuprates are formed when copper salts are added to organohthium reagents [89]. As shown in Scheme 6.56, these reagents, when added to anhydro sugars, readily form new carbon-carbon bonds with ring opening of the epoxide and... 

Yunker, M B, Plaumann, D E, Fraser-Reid, B, The stereochemistry of conjugate addition of lithium dialkyl cuprate reagents to some carbohydrate a-enones. Can. J. Chem., 55, 4002-4009, 1977. Baer, H H, Ong, K S, Raeactions of nitro sugars. IX. The synthesis of branched-chain dinitro sugars by Michael addition. Can. J. Chem., 46, 2511-2517, 1968. 

The synthesis was initiated from the easily available unsaturated aldehyde 60, which reacted with tributyltin cuprate affording a 1,4-adduct (as a mixture of stereoisomers), trapped as trimethylsilyl ethers 61a and 61b. Reaction of these reactive species with synthon 62 afforded the unsaturated precursors of higher carbon sugars 63 and 64. 

Resulting from Cuprates and Sugar-Derived Enones... 

---