Phosphoramidite applications

De Vos, M -J, Cravador, A., Lenders, J.-P., Houard, S, and Bollen, A. (1990) Solid phase non isotopic labelling of oligodeoxynucleotides using 5 -protected aminoalkyl phosphoramidites. Application to the specific detection of human papilloma virus DNA Nucleosides Nucleotides 9, 259-273. 

Substitution-inert complexes have also recently been introduced into DNA as modified-base phosphoramidites. Interest here is generally focused on photo- and redox-active metal species for use as probes for sensing applications (165) and in studies on DNA-mediated electron... 

Cyanine dyes also are used as labels for oligonucleotide probes. Unlike the hydrophilic cyanine dyes valuable for protein labeling, the use of dye-phosphoramidite compounds to synthesize DNA or RNA probes typically requires the use of more hydrophobic dye structures to make them compatible with the solvents and reactions of oligonucleotide synthesis. Thus, indol cyanines containing few or no sulfonates are used in these applications to label oligos for applications such as array detection, hybridization assays, and RT-PCR. 

Since monodentate phosphoramidites are so successful in asymmetric hydrogenation - both because of their performance and their ease of preparation - a logical extension is their application in recyclable systems. Doherty et al. were the first to prepare polymer-supported phosphoramidites by using the monomers 40 and 41 (Scheme 28.12) these led to high ee-values which fell somewhat upon polymerization [78]. The catalyst was shown to be capable of being recycled at least four times. 

In contrast to dehydro a-amino acids, the hydrogenation of acetylated /1-dehy-droamino acid derivatives has only recently been of industrial interest and, accordingly, no applications on a larger scale have yet been reported. Several ligands such as certain phospholanes or phosphoramidites might have industrial potential, but until now these have only been tested on model substrates under standard conditions [50]. Chiral Quests TangPhos and Binapine (Fig. 37.10) have been shown to hydrogenate several acetylated dehydro / -amino acid derivatives with ee-values of 98-99% and TONs of 10000 at r.t., 1 bar [3, 47]. 

The mild conditions offered by the approach of phosphitylation of the anomeric hemiacetals and subsequent oxidation of phosphites to phosphates suggest a very attractive alternative to the 1-0-lithiation method used in lipid A synthesis considering the complexity of the substrates. Indeed, an application of the phosphoramidite methodology was reported to be effective for the stereoselective instalment of the a-anomeric phosphate... 

Phosphoramidites are probably the most versatile ligands in this series as in amidites the substituents at the nitrogen atom are in close proximity to the metal centre and also the substituents could carry chiral centres. In Figure 4.22 we have depicted the simplest derivative, named Monophos , which is highly efficient for asymmetric hydrogenation but for a variety of other reactions as well. The ligand is much easier to make than most, if not all, chiral bidentate phosphine ligands and surely commercial applications will appear. 

Very recently, Ishirihara et al. [237] reported the application of a chiral iodine atom throngh the reaction of NSI and a chiral nucleophilic phosphoramidite for the halocyclization of homo(polyprenyl)arenes. 

The copper-catalyzed enantioselective Michael addition of organometallic reagents to enones was the first successful application of phosphoramidite chiral ligands in catalysis [4, 43]. Since this early report, substantial enhancement of the enantioselectivity and/or of the substrate scope has been achieved through an untiring effort to optimize the ligand structure [5a, 44]. 

Welz et al. developed a procedure for synthesis of oligoribonucleotides based on application of tetrazole for activation of RNA phosphoramidites in automated solid-phase synthesis <2000MB934>. Ar-Benzoyl tetrazole has been developed as a mild and selective reagent for monobenzoylation of the exocyclic amino group in nucleic acid bases <1997TL8811>. An improved procedure is described for the efficient and high yield (76-91%) synthesis of... 

Spiegelmers are a new class of substance for a wide field of applications, especially drug design. Their functional properties can be compared with the action of monoclonal antibodies. The production of spiegelmers is as simple as the synthesis of other oligonudeotides because standard chemical methods, for example common phosphoramidite chemistry, can be employed. 

Modified oligonucleotides, synthesis by phosphoramidite method and application 93T6123. 

The Synthesis of Modified Oligonucleotides by the Phosphoramidite Approach and Their Applications, Beaucage, S. L. Iyer, R. P Tetrahedron 1993, 49, 6123-6194. 

Limbach PA, Crain PF, McCloskey JA. Summary the modified nucleosides of RNA. Nucleic Acids Res. 1994 22 2183-2196. Rozenski J, Crain PF, McCloskey JA. The RNA modification database 1999 update. Nucleic Acids Res. 1999 27 196-197. Beaucage SL, Iyer RP. The synthesis of modified oligonucleotides by the phosphoramidite approach and their applications. Tetrahedron 1993 49 6123-6194. 

A phosphoramidite monomer derived from (71) has been introduced into ODNs for post-synthesis modification. The ketone was treated with a number of aminooxy derivatives, and it was shown that the modification had little effect on duplex stability. This may be used to decorate DNA for a number of DNA applications. A series of modified dUTP analogues (72) which can incorporate a variety of amine derivatives, including biotinylated and fluorescent derivatives, has been prepared for study in PCR reactions. It was found that KOD Dash DNA polymerase was able to incorporate the modified triphosphates during PCR whilst other conventional DNA polymerases would not. 

Kondo, H, Ichikawa, Y, Wong, C-H, (i-Sialyl phosphite and phosphoramidite synthesis and application to the chemoenzymatic synthesis of CMP-sialic acid and sialyl oligosaccharides, J. Am. Chem. Soc., 114, 8748-8750, 1992. 

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