Formylation functions

Acid-induced cyclization of the appropriate (hydroxypropenyl)pyrroles 30, which can be easily derived from a-unsubstituted pyrroles by vinylogous Vilsmeier reaction followed by reduction of the formyl function, yields the corresponding expanded porphyrinogens 31. The... 

Carbohydrates and other biological molecules that contain polysaccharides, such as glycoproteins, can be specifically modified at their sugar residues to produce reactive formyl functionalities. With proteins, this method often allows modification to occur only at specific locals, usually away from critical active centers or binding sites. 

Aldehyde-containing macromolecules will react spontaneously with hydrazide compounds to form hydrazone linkages. The hydrazone bond is a form of Schiff base that is more stable than the Schiff base formed from the interaction of an aldehyde and an amine. The hydrazone, however, may be reduced and further stabilized by the same reductants utilized for reductive amination purposes (Chapter 3, Section 4.8). The addition of sodium cyanoborohydride to a hydrazide-aldehyde reaction drives the equilibrium toward formation of a stable covalent complex. Mallia (1992) found that adipic acid dihydrazide derivatization of periodate-oxidized dextran (containing multiple formyl functionalities) proceeds with much greater yield when sodium cyanoborohydride is present. 

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). 

To interpret these experiments, we suggest that our data point to a stabilizing through-space interaction of a donor olefinic linkage with the formyl function as the likely source of preference of conformers II and III leading to the sense of attack anticipated by the Roush model. [7]... 

H, C6H5) with hydroxide yields a product whose structure was proved to be that of betaine 92. It contains, besides an imino group at position 4 a formyl function at position 5 (Scheme IV.36) (83H1891). 

Another possibility for creating a new ligand structure is to connect two phos-phaferrocene molecules via their formyl functional groups. The reductive coupling of carbonyl compounds with low-valent Ti reagents - the McMurry reaction - is a technique that has found wide application in organic synthesis [18]. 

Treatment of aryl and heteroaryl o-azidocarbaldehydes with bis(trimethylsilyl)sulfide and hydrochloric acid gave fused isothiazoles, via thionation of the formyl function followed by spontaneous decomposition at room temperature. Yield was dependent upon the nature of the heteroaromatic ring. [94CL1873, 94PS479]... 

The highest enantioselectivity is achieved in dioxane, THF, DMF, and NMP (N-methylpyrrolidinone) affording the corresponding /f-formyl functionalized amino acid derivative in high yield and stereoselectivity. The diastereoselectivity of the... 

The addition of carbonylated electrophiles to the 2-lithio derivative of 4-oxazolinyloxazole 132 allowed the efficient preparation of 5-phenyloxazoles 134 bearing a variety of hydroxyalkyl groups at C-2 position and a carboxyl (or formyl) function at C-4. This protocol suppresses the troublesome electrocyclic ring-opening reaction and allows access to the target compounds by simple chemical transformation of the oxazoline moiety of 133 <02JOC3601>. A direct chemoselective C-2 silylation of oxazoles was performed by treatment of the lithiated parent compounds with silyl triflates <02TL935>. 

The Tebbe reagent (4.85) has found applications in reactions of sugars because it methyle-nates carbonyls without racemizing a chiral a-carbon. Thus, methylenation of the formyl functions of 1-0-formylglycoside 4.91 with 4.85 produced 1-0-vinyl glycosides 4.92. 

If the direct anodic oxidation of tertiary formamides, which do not possess an a-hydrogen, is performed, the formyl function is transformed into a carboxymethyl group [233]. 

The stereoselectivity in the reaction of 3-ketofuranose 68 and 2-thiazolyl lithium can be attributed to the kinetic control and steric hindrance from endo-fa.ce addition. The thiazolyl group of compounds 70 and 72 was converted into the formyl functionalized sugars 73 and 74 using essentially a one-pot, three-step literature method [38,39]. 

A new method for the synthesis oligonucleotides containing of 5-formyl-2 -deoxyuridine has been described. The protected phosphoramidite of 5-(l,2-dihydroxyethyl)-2 -deoxyuridine (181) was prepared from 5-iodo-2 -deoxyuridine in seven steps. Following deprotection of the oligomer, subsequent oxidation of the diol with sodium periodate yielded the formyl function which could also be reduced with sodium borohydride to yield the 5-hydroxymethyl compound. An... 

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