Periodate oxidation groups

A more eflicient and general synthetic procedure is the Masamune reaction of aldehydes with boron enolates of chiral a-silyloxy ketones. A double asymmetric induction generates two new chiral centres with enantioselectivities > 99%. It is again explained by a chair-like six-centre transition state. The repulsive interactions of the bulky cyclohexyl group with the vinylic hydrogen and the boron ligands dictate the approach of the enolate to the aldehyde (S. Masamune, 1981 A). The fi-hydroxy-x-methyl ketones obtained are pure threo products (threo = threose- or threonine-like Fischer formula also termed syn" = planar zig-zag chain with substituents on one side), and the reaction has successfully been applied to macrolide syntheses (S. Masamune, 1981 B). Optically pure threo (= syn") 8-hydroxy-a-methyl carboxylic acids are obtained by desilylation and periodate oxidation (S. Masamune, 1981 A). Chiral 0-((S)-trans-2,5-dimethyl-l-borolanyl) ketene thioketals giving pure erythro (= anti ) diastereomers have also been developed by S. Masamune (1986). 

The synthesis of 11-oxaprostaglandlns from o-glucose uses the typical reactions of gl cofuranose diacetonide outlined on p. 267. Reduction of the hemiacetal group is achieved a thioacetal. The carbon chains are introduced by Wittig reactions on the aldehyde grou] which are liberated by periodate oxidation and laaone reduction (S. Hanessian, 1979 G Lourens, 1975). 

Methylation of free OH groups, followed by denitration, hydrolysis, reduction, and glc analysis has been suggested as a method for determining the location of nitrate (82). This method has been suggested for CP and CS (82) as the phosphate and sulfate groups are stable to methylation and can then be removed. Periodate oxidation has been used to determine the DS of CS (81). 

A-Chlorosuccinimide 1 N NaOH." With this method, the sulfide is oxidized completely to the sulfone, which is cleaved with hydroxide more readily than the sulfoxide formed by periodate oxidation. It has been reported that oxidation of the sulfide leads to oxidation of adenine and gua-nine." However, see the discussion of the TPTE group below. 

In theory, periodate oxidation could have given a clear-cut answer as to the composition of the isomeric mixture of deoxy ribose phosphates. The 4-phosphate (73), devoid of vicinal diol groups, should be resistant to periodate the 3-phosphate (74) should reduce one and only one molar equivalent of the oxidant and yield one molar equivalent of both formaldehyde and the phosphorylated dialdehyde (75), whereas the 5-phosphate (76) could be expected to reduce one molar equivalent of periodate relatively rapidly, followed by a slower overoxidation reaction owing to the oxidation of malonaldehyde, formed as a result of the glycol cleavage. 

That the postulated phosphate group migration did in fact, occur, was eventually proved (58) in the following way. During the many experiments done to find conditions in which the phosphate group migration could be demonstrated by periodate oxidation, the conclusion was reached that one of the difficulties in the interpretation of the results was because of the fact that the reaction between the phosphorylated... 

It is, in fact, interesting to note that the latter cyclohexanepentol, which has four adjacent cis-hydroxyl groups, reacts slowly with periodate. Perhaps further light will be thrown on this problem when the results of periodate oxidations of dl-1, 2, 3, 5/4-cyclohexanepentol (36), 1, 2, 4, 5/3-cyclohexanepentol (37), and (1 d)-1, 2, 3/4, 5-cyclohexanepentol (38) will be available. 

For functionalization of S-layer-coated liposomes, the S-layer lattice was stabilized by cross-linking the S-layer subunits with either periodate-oxidized raffinose or bis(sulfo-succinimidyl) suberate (BS ). Both are amine group-specific reagents that were large and... 

Figure 1.107 The N-terminal aldehyde group on a peptide formed from periodate oxidation of serine or threonine residues can be conjugated with a hydrazide-containing molecule to produce a hydrazone bond.

Protein molecule containing periodate-oxidized polysaccharides (having aldehyde groups)... 

Bis-hydrazide-containing molecules also can be used to activate soluble polymeric sub-stances-containing aldehyde groups. For instance, dextran may be periodate oxidized to create numerous formyl functionalities on each molecule. Subsequent reaction with a homobifunctional hydrazide in large excess results in a hydrazide-activated polymer having multivalent-binding capability toward aldehydes or ketones (Chapter 25, Section 2.2). Insoluble support matrices suitable for affinity chromatography have been activated in a similar fashion to create the hydrazide derivative (O Shannessy and Wilchek, 1990). 

The carbonyl-reactive group on these crosslinkers is a hydrazide that can form hydrazone bonds with aldehyde residues. To utilize this functional group with carbohydrate-containing molecules, the sugars first must be mildly oxidized to contain aldehyde groups by treatment with sodium periodate. Oxidation with this compound will cleave adjacent carbon-carbon bonds which possess hydroxyl groups, as are abundant in polysaccharide molecules (Chapter 1, Sections 2 and 4.4). 

Figure 5.12 MPBH reacts with sulfhydryl-containing molecules through its maleimide end to produce thioether linkages. Its hydrazide group then can be used to conjugate with carbonyl-containing molecules (such as periodate-oxidized carbohydrates that contain aldehydes) to give hydrazone bonds.

The hydrazide derivative of AMCA can be used to modify aldehyde- or ketone-containing molecules, including cytosine residues using the bisulfite activation procedure described in Chapter 27, Section 2.1. AMCA-hydrazide reacts with these target groups to form hydrazone bonds (Figure 9.26). Carbohydrates and glycoconjugates can be labeled specifically at their polysaccharide portion if the required aldehydes are first formed by periodate oxidation or another such method (Chapter 1, Section 4.4). 

---