Protective groups, lipophilic

N-Protective -tosyl as - 31, 582 N- and S-Protective -, diphenyl-4-pyridyl as - 25, 417s32 O-Protective -benzyl as - 20, 150 Protective groups, lipophilic 26,104s31... 

This easily prepared lipophilic 5 -phosphate protective group is cleaved by NCS oxidation (dioxane, triethylammonium hydrogen carbonate, 2 h, rt) followed by ammonia-induced j3-elimination. ... 

The lipophilicity of this phosphate protective group helps in the chromatographic purification of oligonucleotides. It is removed by the oximate method. ... 

This highly lipophilic group is cleaved with isoamyl nitrite in Pyr/AcOH. The use of a lipophilic 5 -phosphate protective group aids in reverse-phase HPLC purification of oligonucleotides. 

As mentioned in last year s Report, aromatic phosphoramidates have been used to protect 5 -phosphoryl groups in the stepwise synthesis of oligodeoxyribonucleotides. The appropriate monomer units are coupled with DCC and the phosphoramidate protecting group is removed when required with isoamyl nitrite. A rapid and general preparative method for oligonucleotides has been developed based on phosphoramidates of the highly lipophilic 4-aminophenyltriphenylmethane (25). Purification of... 

An area of considerable research-activity in this field has been the use of highly lipophilic protecting-groups to aid purification, or, alternatively, of substituted ion-exchangers having high affinities for lipo-... 

Fluorous reverse phase silica gel (FRPSG) has been used in the purification of synthetic DNA fragments.In solid phase DNA synthesis, truncated sequences are often separated from the desired product after deprotection using HPLC or electrophoresis. In order to perform, parallel syntheses and separations of nucleotides the trityl-on purification procedure was developed, in which a lipophilic support material is used to separate the desired and undesired product, followed by deprotection. If the protecting group is labelled with a fluorous group, fiuorous-fiuorous interactions between the FRPSG and the protected nucleotide can be used to aid separation of the aqueous mixture. 

The presence of the unsaturated undecaprenylside chain makes lipids I and II challenging synthetic targets. As a key strategy for the synthesis of lipid I (21), the undecaprenyl-linked diphosphate moiety was infroduced at a late stage in the synthesis to avoid potential solubility complications caused by the enhanced lipophilic character of the undecaprenyl-linked substrate. The anticipated acid sensitivity of the anomeric diphosphate dictated the use of base-cleavable protective groups for all peripheral functionality, including the side chains of peptapeptide. 

Protection of 5 -phosphate group in synthesis of dinucleotides. The 5 -phosphate group of mononucleotides is converted into 5 -esters by reaction with (I) in the presence of triisopropylbenzenesulfonyl chloride (TPS 1, 1228-1229 3, 308) or DCC. The esters are then condensed with a 3 -0-acetylated mononucleotide in pyridine with TPS to form TPTE-dinucleotides in 50 0% yield. The value of (1) is that it confers lipophilic properties on the protected dinucleotides so that they can be extracted into ethyl acetate-butanol or methylene chloride-butanol. The protecting group is removed by oxidation to the corresponding sulfone (NCS) and -elimination. 2-(p-Tritylphenyl)sulfonylethanol (TPSE) can be used in place of (1) in this event, the oxidation step is not necessary. A number of tri-and tetranucleotides were also prepared by this new method. ... 

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