3 -Deoxy derivatives

R" = -H, 5-0-carbamoyl-2-amino-2-deoxy-L-xylonic acid or the 3-deoxy derivative... 

The only recorded example using this method in the sugar series is the chlorination of l,2 3,4-di-0-isopropylidene-D-galactopyranose (73) which affords in addition to the expected 6-chloro-6-deoxy derivative 74a, a 5,6-unsaturated derivative 75 as well. These products were separated by silica gel column chromatography no yields were given. 

Several other methods for the introduction of halo atoms at C-6 in hexose derivatives have been known since the late 1920s. One of the earlier methods involved the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-glucopyranoside with phosphorus pentachloride which resulted only in an 8% overall yield of methyl 6-chloro-6-deoxy-a-D-glucoside (57). In contrast, the reaction of methyl 2,3,4-tri-0-acetyl-6-0-trityl-a-D-altropyranoside with phosphorus tribromide and bromine afforded a 73% yield of the corresponding 6-bromo-6-deoxy derivative (91). 

The 2-deoxy derivative (215) of 202 was prepared from the diacetate 213, obtained by debromination of 34, following a similar sequence starting from the dibromide 214. 

With yS-D-glucosidase A3 from Asp. wentii, the conversion of ) -D-gluco-sides into the 2-deoxy derivatives had a much larger effect on k3 than on k2, so that deglycosylation became rate-limiting. As a consequence of the... 

A series of mono- and di-deoxy derivatives of methyl a-D-glycopyrano-... 

Derivatives 47-51 were prepared from the iV-oxide 46 using zinc as the deoxygenating agent (Scheme 11). The use of Zn in NH4CI solution led to the deoxy derivatives 47 and 48 in moderate yields. The reduction was clearly observed by NMR HETCOR experiments (HMQC and HMBC). When the reduction of the derivative 46 (R = CH2C1) was carried out under the same conditions, compound 51 was generated via a Zn-promoted reductive dimerization process <2001EJM771>. 

The interesting observation has been made that 3 -amino-3 -deoxy-adenosine as a suspension in phosphoryl chloride-triethyl phosphate at 4° is converted into the 5 -chloro-5 -deoxy derivative in 80% yield, but that predissolution of the nucleoside in triethyl phosphate, followed by treatment with phosphoryl chloride at 0°, yields the 5 -phosphate in 62% yield.382... 

The reaction of methyl a-D-glucopyranoside with sulfur monochloride in N,N-dimethylformamide to give the 6-chloro-6-deoxy derivative in 30-35% yield has been described392 it is possible thatN,N-... 

In contrast to uridine,389 cytidine does not yield a 5 -chloro-5 -deoxy derivative on reaction with N,N-dimethyl(chlorometh-animinium) chloride instead 2,2 -anhydrocytidine is formed.395 However, thionyl chloride or bromide in hexamethylphosphor-amide at room temperature achieves this selective replacement of the primary hydroxyl group of halogen in cytidine, and also in adenosine, in respective yields of 80 and 75% for the chloro compounds, and 55 and 30% for the bromo analogs.396... 

Intramolecular displacement of primary sulfonyloxy or halide groups in derivatives of D-mannitol can also be brought about under basic conditions, albeit in low yield. Treatment of l,6-di-0-(methyl-sulfonyl)-D-mannitol (78), or the corresponding dichloride derivative, with sodium methoxide gave 2,5 3,6-dianhydro-D-glucitol74 (79). Treatment of the latter with hydrochloric acid at 100° in a sealed tube gave the 6-chloro-6-deoxy derivative (80), which was converted into the known 2,5-anhydro-l,6-di-0-benzoyl-D-glucitol45 47 (32). The sequence 78-80 is of interest in the context of C-/3-D-nucleoside precursors, but it suffers from the fact that yields are low. 

The reaction of sulfuryl chloride with carbohydrates to give chloro-deoxy derivatives has been reviewed briefly in this Series.98 The reaction of sulfuryl chloride with monosaccharides has been shown to afford products in which the secondary hydroxyl groups are replaced by chlorine with inversion of configuration.68-75 Jones and coworkers reported that the reaction of methyl a-D-glucopyranoside with sulfuryl chloride and pyridine in chloroform at room temperature proceeds by way of the 4,6-bis(chlorosulfate) by an Sn2 process, with chloride as the nucleophile, to give methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-bis(chlorosulfate).74... 

The role of the kinetic anomeric effect was demonstrated by the difference in diastereoselectivities observed for the addition of LiP03Me2 to IV-glycosylnitrone 51 and to the deoxy analogue 52. In TFIF, the difference in diastereoselectivities corresponds to a value of 1.1 kcal/mol while in CH2CI2 it gives a value of 0.6 kcal/mol. Moreover the deoxy derivative 52 undergoes a slower reaction than its parent glycosylnitrone 51. 

Figure 9.12 Deoxy derivatives. These contain one less oxygen atom than the monosaccharide from which they are derived. 2-Deoxyribose is a most important deoxy pentose and is a major constituent of deoxyribonucleic acid (DNA). Deoxy hexoses are widely distributed among plants, animals and microorganisms especially as components of complex polysaccharides. Examples are rhamnose (6-deoxymannose), a component of bacterial cell walls, and fucose (6-deoxygalactose), which is often found in glycoproteins and is an important constituent of human blood group substances.

Sucrose Ethers. Being next to the anomeric center and intramolecularly hydrogen-bonded, the 2 -OH of sucrose is the most acidic, which means it is deprotonated first under alkaline conditions, and thus preferentially yields to etherification. Benzylation with NaH/benzylbromide in DMF, for example, results in an 11 2 1 mixture of 2 -(9-benzyl-sucrose (Figure 2.8) and its 1-0- and 3 -0-isomers. Because the former is readily accessible, it proved to be a versatile intermediate for the generation of 2 -modified sucroses, for example, the 2 -keto and 2 -deoxy derivatives as well as sucrosamine (2 -amino-2 -deoxy-sucrose), whose application profiles remain to be investigated. 

Lichtenthaler, F. W. Immel, S. Pokinskyj, P. Selective 2-O-benzylation of sucrose. A facile entry into its 2-keto- and 2-deoxy derivatives and to sucrosamine, Liebigs Ann. Chem., 1995, 1938-1947. 

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