Glucose-derived ketone

The dioxirane epoxidation of a prochrral alkene will produce an epoxide with either one new chirality center for terminal alkenes, or two for internal aUcenes. When an optically active dioxirane is nsed as the oxidant, expectedly, prochiral alkenes should be epoxi-dized asymmetrically. This attractive idea for preparative purposes was initially explored by Curci and coworkers in the very beginning of dioxirane chemistry. The optically active chiral ketones 1 and 2 were employed as the dioxirane precursors, but quite disappointing enantioselectivities were obtained. Subsequently, the glucose-derived ketone 3 was used, but unfortunately, this oxidatively labile dioxirane precursor was quickly consumed without any conversion of the aUcene . After a long pause (11 years) of activity in this challenging area, the Curci group reported work on the much more reactive ketone... 

The substrate scope was expanded to cis-olefins and certain terminal olefins when a new series of glucose-derived ketones 4 and 5 were developed. In 2000, Shi reported an A -Boc oxazolidinone-bearing ketone 4 to be a highly enantioselective catalyst for the epoxidation of various cis-olefins conjugated with an aromatic or alkyne group. The stereopreference of the olefin appears to be directed by an attraction fi om the oxazolidinone moiety of ketone 4. In the transition state, Rrt substituent on the substrate prefers to be proximal to the oxazolidinone of ketone 4 (spiro C favored over spiro D). ... 

In efforts to expand the scope of the ketone catalyzed epoxidation, glucose-derived ketone 57 was reported to be an effective catalyst for the epoxidation of ds-olefms in 2000 (Scheme 3.44). High ee can be obtained for a number of both acychc and cyclic olefins (Scheme 3.44) [76-79]. The epoxidation is stereospecific and no isomeriza-... 

In 2002, Shing and coworkers reported three glucose derived ketones 58-60 as epoxidation catalysts (Scheme 3.46) [81]. Ketone 58 was found to be more effective than 59 and 60, and up to 71% ee was obtained for stilbene with this ketone. In 2003, Shing and coworkers reported their studies on epoxidation with the L-arabi-nose derived ketones 61-64 (Scheme 3.47) [72]. Up to 90% ee was obtained for stilbene with 64. Further studies showed that a higher yield of the epoxidation could be obtained with the ester substituted ketones 65-67, and up to 68% ee was obtained for phenylstilbene (Scheme 3.48) [72]. 

In 2002, Shing et al. reported glucose-derived ketones 391 and 392. Ketone 391 epoxidizes tran -stilbene with up to 71% ee [277]. A series of L-arabinose-derived ketones 393-399 followed, and up to 90% ee was obtained for tran -stilbene epoxide with ketone 396 [278], In the same year, Zhao et al. reported three fructose-derived ketones and aldehydes 400-402 for the asymmetric epoxidation [279], Aldehyde 402 achieved 94% ee for tran -stilbene. hi 2009, Davis et al. presented a variety of conformationally restricted ketones 403, prepared from A-acetyl-D-glucosamine which show useful selectivities with terminal olefins (styrene 81% ee. Fig. 7.19) [280]. 

Glucose derived from gluconeogenesis to ketones derived from fatty acids ( 1 week)... 

In the fed state, the only fuel used by the brain is glucose, derived from the blood. In prolonged starvation or chronic hypoglycaemia, ketone bodies are nsed which rednce the rate of utilisation of glucose by the brain bnt, even so, glucose still provides about 50% of the energy. Consequently, under all conditions, maintenance of the blood glucose concentration is essential for the function of the brain the mechanisms that are responsible for this are discnssed in Chapters 6, 12 and 16. 

We reported a catalytic enantioselective cyanosUylation of ketones that produces chiral tetrasubstituted carbons from a wide range of substrate ketones [Eq. (13.31)]. The catalyst is a titanium complex of a D-glucose-derived ligand 47. It was proposed that the reaction proceeds through a dual activation of substrate ketone by the titanium and TMSCN by the phosphine oxide (51), thus producing (l )-ketone cyanohydrins ... 

We began our synthesis by finding the optimum reaction conditions for the catalytic asymmetric cyanosilylation of ketone 28 (Table 1). Based on previous studies,30 the titanium complex of a D-glucose derived ligand (catalyst 32 or 33) generally gives (/ )-ketone cyanohydrins, which is required for a synthesis of natural fostriecin. 

Glucose,123 and terpene derived ketones,124 have been used as chiral auxiliaries for the formation of new stereogenic centres by a similar method 123... 

The bifunctional catalysts developed by Shibasaki and coworkers effective in the asymmetric cyanation of aldehydes and ketones (see Section 6.2) have been applied to good effect in the cyanation of imines. For instance, aluminium BINOL (6.65) catalyses the cyanation of aromatic and a,p-unsaturated N-fluorenylaldimines using TMSCN in good ee, while gadolinium complexes of the glucose-derived ligand (6.71) and derivatives have been used in the enantioselective cyanation of ketimines. ... 

Reduction of ketones with sodium borohydride in the presence of a carboxylic acid and 1,2 5,6-di-0-cyclohexylidene-a -D-glucofuranose gave 35-50% enantiomeric enhancement values.Another group has reported a similar reaction with the corresponding di-O-isopropylidene-glucose derivative and prochiral aromatic ketones. Optical yields of up to 64% were claimed. The chiral reagents appear to be sodium acyloxyborohydrides, which complex with the carbohydrate before reduction takes place. 

Several olha- syntheses of cyclohexane-containing natural products reported also utilized Fenier rearrangement as a key step. A synthesis of a compactin analogue involved conv aon of the 1,6-anhydro-D-glucose-derived 44 to cyclohexanone 45, which was further elaborated to 46 en route to die natural product, via elimination, stereoselective ketone reduction, cuprate methyl Sn2 ... 

J)-3-Hydroxyleucine 313 has been prepared from D-glucose via known ketone 312. Dipeptide isosteres 315 (e.g. Y=CH2Ph, X=OMe, R =Boc, R =Bn) are available from D-glucose-derived 314. ... 

---