烷氧基甲基醚或烷氧基取代甲基醚在羟基保护中也是较为多用的一类，常用的有THP (2-四氢吡喃)，MOM（甲氧基甲机基），EE（2-乙氧基乙基），这类保护基都对酸不稳定，因此一般都是脱保护。它们对酸的稳定性是MOM>EE>THP。

THP (2-四氢吡喃)保护羟基

       THP 醚引入到一个手性分子的结果是形成了一个非对映体，因为在四氢吡喃环上新增了一个手性中心。（有时它会使NMR 谱的表达有点困难）。尽管如此， 它仍是有机合成中一个非常有用的保护基团，它的成本低，易于分离，对大多数非质子酸试剂有一定的稳定性，易于被出去。通常，几乎任何酸性试剂或任何可以在原位产生酸的试剂都可被用来引入THP 基团。

THP (2-四氢吡喃)保护羟基示例

      To a solution of 1 (1.5 g, 3.5mmol) in CH2Cl2 (10 mL) at 22-24oC was added 3,4-dihydro-2H-pyran (0.479 mL, 0.442 g, 5.25mmol) and PPTs (20 mg, 0.08mmol). The solution was stirred at 22-24oC for 1 h and diluted with a 100-mL solution of (1:1) diethyl ether and ethyl acetate. The organic layer was separated, washed with H2O (3 × 100mL), and the residue was chromatographed, eluting with hexane/ethyl acetate (20:1) to give the THP ether 2 as clear oil (1.75 g, 97%).

THP (2-四氢吡喃)脱保护示例

     To an ethanol solution (30 mL) of THP ether 1 (1.87 g, 5mmol) was added PPTS (20 mg,0.08mmol) in one portion. The solution was refluxed for 1 h, cooled to 22-24oC, and diluted with a mixture of diethyl ether (100 mL) and H2O (200 mL). The organic layer was washed with H2O (2 × 100mL), dried over Na2SO4 and concentrated in vacuo. The residue was purified by chromatography on silica gel, eluting with hexane/ethyl acetate (3:1) to give 2 (1.36 g, 94%) as clear oil.