Alloc group

Allylamines are difficult to cleave with Pd catalysts. Therefore, amines are protected as carbamates, but not as allylamines. Also, allyl ethers used for the protection of alcohols cannot be cleaved smoothly, hence alcohols are protected as carbonates. In other words, amines and alcohols are protected by an allyloxycarbonyl (AOC or Alloc) group. 

BuMc2SiH, Pd(OAc)2, CH2CI2, Et3N, 100% yield. Cbz groups and Alloc groups are also cleaved, but benzyl ethers are stable. 

The Alloc group can be converted to a silyl carbamate that is readily hydrolyzed. ... 

Pd(Ph3P)4, RS02Na, CH2CI2 or THF/MeOH, 70-99% yield. These conditions were shown to be superior to the use of sodium 2-ethylhexanoate. Methallyl, crotyl, and cinnamyl ethers, the Alloc group, and allylamines are all efficiently cleaved by this method. ... 

Pd(OAc)2, TPPTS, CH3CN, H2O, 75 min. 100% yield. The Alloc group is readily released in the presence of this ester. 

Pd(Ph3P)4 and Bu3SnH convert the Alloc group to other amine derivatives when electrophiles such as (B0C)20, AcCl, TsCl, or succinic anhydride are added. Hydrolysis of the stannyl carbamate with acetic acid gives the free amine. 

The readily prepared immobilized phosphoramidite could be used to efficiently synthesize oligodeoxyribonucleotides with modified thymidine residues. Whereas the effect of microwave irradiation on the deprotection by exposing the strand to tet-rakis-triphenylphosphine palladium(O) and diethylammonium bicarbonate was only small using dichloromethane as solvent, complete removal of the alloc group was achieved in N,N-dimethylformamide within 10 min at 80 °C (Scheme 7.30). After the reaction, the solid-supported product was washed with N,N-dimethylformamide and dichloromethane and dried, before being subjected to acylation. The coupling... 

Deprotection of the A -alloc group of A -imidazoline 1056 with Pd(PPh3)4 catalyst gives cleanly the desired product 1075 if a basic allyl acceptor is used. In contrast, a mixture of 1057 and 1058 is formed when the acidic allyl acceptor dimedone is used (Scheme 254) <1997TL4359>. 

In the J-resolved projection, the aromatic rings of the SCAL are clearly present where as the polymer resonances have dropped out of the spectrum. In addition, the proton coupling constants arising from alloc group are readily measured as seen in the expanded spectrum (Fig. 13). If a more detailed measure of the couplings is desired, then the full 2D J-resolved spectrum can be evaluated in the normal manner as exemplified in Fig. 14. A similar method to obtain accurate proton-proton coupling constants based on E.COSY spectra has also appeared recently (43). 

Ph3P)2NiCl2,3% PhjP, MejNH-BHj, K2CO3, CHjCN, 40°C, 82-97% yield. Aryl Cbz groups are also cleaved but at a slower rate. The Alloc group can be cleaved in the presence of a Cbz. 

A comparison of the Alloc group to the Preoc group shows that the Alloc group is more easily cleaved, but an extensive investigation has not been done. 

The use of PNZ derivatives in conjunction with Fmoc chemistry results in fewer problems with aspartamide and diketopiperazine formation and it is superior to the use of the Alloc group for ornithine and lysine protection in Fmoc based peptide synthesis."... 

Another instance for this linker class is the safety-catch linker by Lyttle, which was developed for the synthesis of nucleic acids on solid supports [62]. Starting from a resin carrying an Alloc-protected amino group fragment, conventional phosphoramidite chemistry was carried out to build up the desired immobilized nucleotide 57. Removal of the Alloc group via palladium catalysis under neutral conditions produces a polymer-bound intermediate 58 with a free amino functionality that can intramolecularly attack activated phosphonates and liberate the nucleotide 59 from the solid support (Scheme 16.14). More examples of safety-catch linkers that use the deprotection of an N-functionality as the activation step are listed in Table 16.1 (resins 61-65) [63-68]. 

Both allyl esters and Na-allyloxy carbonyl (Alloc) groups can be cleaved using palladium-catalysed hydrostannolysis by tri-n-butyltin... 

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