Triethylamine protecting group

The trimethylsilyl protecting group can be removed by routine deprotection with triethylamine -hydrogen fluoride complex. 

The triethylamine hydrochloride formed in step (a) serves as an activator in step (b) for the reaction with an alcohol (ROH) providing the phosphite containing the desired protecting group. Acetonitrile proved to be a better solvent for this reaction than dichloromethane. It was found that activation by pyridinium hydrochloride was faster but led to formation of dinucleoside phosphite. 

Ring closure of (3-hydroxy-a-amino acids with sulfuryl chloride/triethylamine 68 is accompanied by formation of (3-chloroalanine,16 1 whereas cyclization of urethane-protected serine and threonine by the Mitsunobu reaction 54 69 70 leads to oxazoline and dehydroalanine formation as side products. 47,71 Formation of dehydroalanine can be prevented by bulky carboxy protecting groups such as tert-butyl esters. 69 ... 

Since the electrophile is introduced adjacent to the NH protective group, substantial steric hindrance may be encountered in the following reaction steps. In case of the dimethylsulfamoyl protected imidazole-5-carboxaldehyde, a rapid isomerisation to the 4-substituted product can be induced catalytically by traces of triethylamine or by mere standing at RT for several days42. The effect of steric hindrance by the protective group was also observed in the reduction of ethyl dimethylsulfamoyl-imidazolecarboxylate with DIBAH. The 5-isomer could not be reduced, whereas the 4-isomer is reduced easily to the imidazole carboxaldehyde under the standard conditions49. 

R)-Arbutamin was produced as follows 89.3 mg of (-)-l-di(t-butyldimethylsiloxy)phenyl)-2-aminoethanol, 50.0 mg of 4-(4-methoxymethoxyphenyl)butanoic acid, diethylphosphorylcyanide, and triethylamine were dissolved in N,N-dimethylformamide at 0°C, reacted at room temperature, so as to obtain 108.6 mg (in a yield of 82%) of amide compound. The amide compound obtained was reduced lithium aluminium hydride in an ether solvent at reflux temperature, so as to quantitative obtain amine. And 55.6 mg of (R)-arbutamin which is intended compound was obtained by deprotecting the hydroxyl-protecting group of amine in a methanol-THF solvent at room temperature using hydrochloric acid. 

We can also easily convert hydroxyl groups to silyl ethers. Section 14-10B covered the use of the triisopropylsilyl (TIPS) protecting group for alcohols. Similarly, sugars can be converted to their silyl ethers by treatment with a silyl chloride, such as chlorotrimethylsilane (TMSC1), and a tertiary amine, such as triethylamine. 

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