LiAIH

The trick used is to acylate the amine instead, since we can reduce the resulting amide with LiAIH, to give the product we want ... 

Common reducing agents are hydrogen in the presence of metallic or complex catalysts (e.g. Ni, Pd, Pt, Ru, Rh), hydrides (e.g. alanes, boranes, LIAIH, NaBHJ, reducing metals (e.g. Li, Na, Mg, Ca, Zn), and low-valent compounds of nitrogen (e.g. NjHj, NjHJ, phosphorus (e.g. triethyl phosphite, triphenyiphosphine), and sulfur (e.g. HO-CHj-SOjNa = SFS, sodium dithionite = Na S O. ... 

Hydrides are available in many molecular sizes and possessing different reactivities. LiAIH reduces most unsaturated groups except alkenes and alkynes. NaBH is less reactive and reduces only aldehydes and ketones, but usually no carboxylic acids or esters (N.G. Gaylord, 1956 A. Haj6s, 1979). 

The benzyl group has been widely used for the protection of hydroxyl functions in carbohydrate and nucleotide chemistry (C.M. McCloskey, 1957 C.B. Reese, 1965 B.E. Griffin, 1966). A common benzylation procedure involves heating with neat benzyl chloride and strong bases. A milder procedure is the reaction in DMF solution at room temperatiue with the aid of silver oxide (E. Reinefeld, 1971). Benzyl ethers are not affected by hydroxides and are stable towards oxidants (e.g. periodate, lead tetraacetate), LiAIH, amd weak acids. They are, however, readily cleaved in neutral solution at room temperature by palladium-catalyzed bydrogenolysis (S. Tejima, 1963) or by sodium in liquid ammonia or alcohols (E.J. Rcist, 1964). 

Scheme 1-31. Elsenbaumer route to dimethoxy PTV 92 a) Me2S04 b) LiAIH, TF c) PhSH, Znl2 d) MCPBA, CHCI3 e)KOtBu. THF f) 80 C.

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