Benzyl deprotection using

Hydrogenation is widely used for deproteetion of benzyl and benzyloxycarbonyl groups. Kappe s group [67,68] deprotected benzyl esters using continuous flow and then performed comparative experiments using conventional heating and microwave assisted transfer hydrogenation, whieh resulted in lower yields (53-65%) than when eompared to flow (80-85%). 

The reaction shown in Scheme 25 has been successfully used to deprotect Al-benzylic carboxamides using water as the quenching reagent, after the naphthalene-catalyzed lithiation . 

Tr ping of these soH Ued dipole-stabilized anions with eitho oxygen or the complex of oxodiper-oxymolybdenum with HMPA and pyridine gives honiaminals which provide secondary amides. The procedure can therefore be used as a method of benzyl deprotection of amides (equation 31). 

Aminotriazine derivatives 35 are available in two steps by treating ohlorotriazines 33 with acid-labile benzylic amines including triphenylmethylamines, diphenylmethylamines or 2,4-dimethoxybenzylamine 34, followed by deprotection using trifluoroaoetio acid <05TL2005>. 

The total synthesis of ditryptophenaline (651) used stereoisomer 637, which was oxidized (—> 645) and reduced to give diol 646 (Scheme 10.5). Analogous to the previously described synthesis, 646 was subjected to a Mitsunobu reaction and reduction to furnish cyclization product 647. Benzyl deprotection and coupling with a Fmoc-protected W-methyl-(5)-phenylalanine derivative yielded tetrapeptide 648. TMSE-deprotection, two oxidations (—> 650), Fmoc-deprotection, and DCC-mediated cyclization finally led to the natural product ditryptophenaline (651). 

Similar strategy has been applied to obtain l, 2,3,3, 4,4 -hexa-0-benzylsucrose (7). In the first step, TBDPSCl (2.2 equiv.) was used to obtain 6,6 -di-0-TBDPS-suerose 5, whieh was subsequently benzylated to obtain 6. The primary positions were then seleetively deprotected using TBAF, to give compound 7 in good yield (65% or 21% overall from sucrose). 

S-benzyl-(S)-[ H/ C]cysteines were chemically deprotected using sodium/liquid ammonia to obtain the corresponding [ H/ C]cysteines. ... 

Section 27 16 Carboxyl groups are normally protected as benzyl methyl or ethyl esters Hydrolysis m dilute base is normally used to deprotect methyl and ethyl esters Benzyl protecting groups are removed by hydrogenolysis... 

CF3CO2H, PhSCH3, 25°, 3 h. ° The use of dimethyl sulfide or anisole as a cation scavenger was not as effective because of side reactions. Benzyl ethers of serine and threonine were slowly cleaved (30% in 3 h complete cleavage in 30 h). The use of pentamethylbenzene had been shown to increase the rate of deprotection of 0-Bn-tyrosine. ... 

Pd/C, H2, EtOAc, >52% yield. The p-phenylbenzyl ether is more easily cleaved by hydrogenolysis than are normal benzyl ethers. This property was used to great advantage in the deprotection of the following vineo-mycinone intermediate ... 

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