Protections hydroxyl groups

Reduction with (/-Bu)2AlH affords a diol, with one hydroxyl group protected as a MOM group. The more substituted hydroxyl bears the MOM group. ... 

In a prostaglandin synthesis, a carbonyl group was protected as an oxime that had its hydroxyl group protected against Collins oxidation by the phenyl-thiomethyl group. The phenylthiomethyl group is readily removed to give an oxime that is then cleaved to the carbonyl compound. ... 

Hydroxyl groups protected as acetonides or as silyl, tetrahydropyranyl, benzyl, or methoxymethyl ethers are stable to these conditions. Yields with KMn04 are higher than those obtained with KMn04 and dicyclohexyl- 18-crown-6, Bu4NMn04, or NaMn04H20. ... 

Aldonolactones having their hydroxyl groups protected as ethers (mainly benzylated and silylated derivatives) have been employed for chain elongation through the carbonyl group, and therefore these type of derivatives are included in Section V. 

The chiral cyanohydrins also lead directly to a-hydroxy acids by hydrolysis (sequence B) [69] and to protected a-hydroxy aldehydes by first hydroxyl group protection, followed by reduction of the nitrile and hydrolysis of the intermediate imine (not shown) (sequence C) [114]... 

Ethyl vinyl ether is also useful for hydroxyl-group protection. The resulting derivative (1-ethoxyethyl ether) is abbreviated as the EE group.5 As with the THP group, the EE group contains a stereogenic center. 

The solid-phase synthesis of oligosaccharides is usually performed using acid-resistant linkers and protective groups, because of the slightly acidic reaction conditions required for glycosylations (Section 16.3). Hydroxyl group protection is conveniently achieved by conversion into carboxylic esters, such as acetates, benzoates, or nitro-benzoates. Support-bound esters of primary or secondary aliphatic alcohols can be cleaved by treatment with alcoholates [97-99] (Table 7.8), with DBU in methanol, with hydrazine in DMF [100] or dioxane [101], or with ethylenediamine [102], provided that a linker resistant towards nucleophiles has been chosen. 

Hydroxyl group, protection of, 10-142 as esters, 87-118 Reactivity Chart 2, 417-420 as ethers, 14-87 ... 

The benzyloxycarbonyl group (Cbz or Z) is useful in carbohydrate syuithesis, not only for IV-protection of amino sugars, but also to protect alcohols [262,263]. The main advantage of this group is that it is cleaved by hydrogenolysis, and when compared to benzyl ethers, benzyl carbonates are not only removed more readily [264] but also allow hydroxyl group protection under softer conditions than those employed for benzylation. 

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