Amines allyloxycarbonyl

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. 

PdCl2(Ph3P)2, dimedone, THF, 95% yield. This method is also effective for removing the allyloxycarbonyl group from alcohols and amines. 

Synthesis of l,2-frans-2-Acetamido-2-deoxyglycosyl Amino Acids Using Carbamate (2,2,2-Trichloroethoxycarbonyl or Allyloxycarbonyl) Protection of the Amine... 

Glycosidation of D-glucosamine. N-Allyloxycarbonyl derivatives of amines are obtained by reaction with 1 and N(C2H5)3. This derivative (2) of triacetyl-D-glucosamine undergoes selective p-glycosidation by virtue of anchimeric assistance.1... 

Various other types of amine protection have been investigated as replacements for the native V-acetyl group in sialyl donors including Boc [54], allyloxycarbonyl [55], 9-fluorenylmethylcarbonyl [55], trichloroacetyl [55], and Cbz [55, 56] groups, but no particular advantages of these systems are apparent at present. 

Then, we have investigated the cleavage of allylcarbamates (Table 2). The reaction was first conducted on primary amines in homogeneous medium. Under treatment with mol 2 % of Pd(0) catalyst and 2.2 eq. of nucleophile N-Allocbenzyl-amine 7 was quantitatively cleaved to recover the parent molecule within 10 minutes (entry 1). However, when N-allyloxycarbonyl-N-methyl benzylamine 8 was allowed to react under the same conditions, the undesired reaction of N-allylation... 

This efficient and unexpensive methodology thus allows the removal of allyl and allyloxycarbonyl groups from various substrates and the particularly mild conditions are compatible with polyfiinctionalized molecules. Moreover, both Pd(0) catalyst and N-allyl diethylamine by-product are easily separated from the free alcohols, amines and carboxylic acids which are recovered in almost pure form. 

The catalytic system can be recycled up to 10 times as presented in the following scheme (the procedure is applied on N-methyl N-allyloxycarbonyl benzylamine), without loss of efficiency. After completion of the reaction, the first schlenck tube containing the free amine in the organic layer and the catalyst in the aqueous layer is linked, by a siphon tube, to another schlenck tube containing the protected amine dissolved in butyronitrile. The aqueous layer with the active catalyst is transferred under argon pressure into the second tube, over the fresh solution of N-allyloxycarbonyl-N-methyl benzylamine. 

Reductions. iyn-Selective reduction of observed with borane-pyridine in the present predominate in the reduction with LiBHEt-.-C (Ph,P)4Pd catalyzes removal of the R SC the transformation of y,8-epoxy-o(,p-un.saiurj lers by the borane-dimethylamine complex Allyl group scavengers. In the solid-nitrogen by an (V-allyloxycarbonyl group can the presence of a borane-amine complex. 

Peptide synthesis.- An Ai-allyloxycarbonyl derivative of an a-amino acid is deblocked by a combination of PhSiH and a Pd catalyst. When an activated ester of another amino acid is present, it will be attacked by the released amine. 

Another useful strategy for the activation of an amide towards hydrolysis involves intramolecular 0-alkylation of the amide carbonyl. An early rendition of this strategy entailed the use of 4-chlorobutanamides in which cleavage was initiated by treatment with silver(I) perchlorate in aqueous acetone. More re-cently the Fraser-Reid group showed that N-pent-4-enoyl derivatives are rapidly and efficiently cleaved under mild conditions by brief treatment with 3 equivalents of iodine in aqueous THF [Scheme 8.29]. These deprotection conditions do not affect oxidisable functionalities including p-methoxybenzyl ethers and alkyl sulfides though allyloxycarbonyl groups appear to be incompatible. Primary and secondary amines are readily protected as N-pent-4-enoyl derivatives by reaction with pent-4-enoic anhydride. 

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