Amino phenylsilane

Allyl carbamates also can serve as amino-protecting groups. The allyloxy group is removed by Pd-catalyzed reduction or nucleophilic substitution. These reactions involve formation of the carbamic acid by oxidative addition to the palladium. The allyl-palladium species is reductively cleaved by stannanes,221 phenylsilane,222 formic acid,223 and NaBH4,224 which convert the allyl group to propene. Reagents... 

A large number of different a,(o-bis[(trifluoromethyl)sulfonyloxy]-substituted organosilicon compounds can be obtained by relatively simple methods from the corresponding amino-, allyl-, or phenylsilanes. Moreover, it is remarkable that these silyl triflate derivatives are often easily formed, when the synthesis of the corresponding chloro- or bromosilanes is difficult or does not appear to have been attempted. Eq. 2 and Eq. 3 show selected examples of this synthesis [10-12]. The products were prepared in high purities and yields. The resulting triflates should be used for the polycondensation without further purification, because they often cannot be destilled without decomposition. 

A special one-pot deprotection-transacylation method involves coupling of activated Fmoc amino acids with Aloc-protected amino acid esters.The Aloc-deprotection proceeds with palladium/phenylsilane in the presence of the acylating species. Using Fmoc-Phe-F the synthesis of the sterically demanding dipeptide Fmoc-Phe-(Me)Aib-OMe was accomplished in a yield of 65% A similar one-pot approach to the acylation of the even more difficult hindered and weakly nucleophilic a-trifluoromethyl amino acid esters involves the intermediate A-Teoc protection. Thus treatment of ( )-Teoc-a-(a-CF3)Leu-OMe with Fmoc-Gly-F and a catalytic amount of tetraethylammonium fluoride in acetonitrile at 50 °C for 1-2 weeks gave ( )-Fmoc-Gly-(a-CF3)Leu-OMe (77%... 

Another example is H-Thr(tBu)-Gln(Trt)-Ile-Asp(OtBu)-Ser(tBu)-Pro-Leu(A -Aloc)-Dap-MBHA-resin, synthesized by the Fmoc strategy.P l Following cleavage of the Aloe group with phenylsilane and tetrakis(triphenylphosphine)palladium, two (aminooxy)acetyl moieties were linked to the a-amino groups of Thr and Dap by reacting the peptide-resin with [(A-Boc-amino)oxy]acetyl A-hydroxysuccinimide ester. 

Hydrodehalogenation. Phenylsilane is a convenient reagent for radical dehalogenation (e.g., removal of bridgehead halogen atoms), whereas the combination of McjSiH and LiAlH is useful for the conversion of 2-apoisopinocampheyldihaloboranes to the monohalo derivatives.- For A -methylation of amino acids via 2,2-bis(trifluoromethyl)oxazolidin-5-ones, the treatment with formaldehyde-thionyl chloride leads to the A-chloromethyl derivatives which undergo dechlorination by... 

For the deprotection of the allyl group (Glu(OAll)), prepare a solution containing phenylsilane (PhSiHs) (14 equiv. with respect to the loaded amino acid), Tetrakis(triphenylphosphine) palladium(O) (Pd(PPh3)4) (0.05 equiv. with respect to the loaded amino acid—see Note 16) in THF (30 mL for 1 mmol of loaded amino acid). 

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