MOM（甲氧基甲基醚）是一種保護(hù)羥基的常用方法；其對(duì)酸還是較為穩(wěn)定的，一般它的脫除需要在強(qiáng)酸條件下進(jìn)行。
保護(hù)條件：
一、CH3OCH2Cl（MOMCl），DIEA，在二氯甲烷中，0℃到室溫，反應(yīng)8h，在引入MOM時(shí)，此條件是最常用的方法。但是MOMCl是致癌物，而且在制備MOMCl時(shí)產(chǎn)生的二氯甲基甲基醚毒性更強(qiáng)。因此在使用MOMCl時(shí)要做好防護(hù)措施。
MOM(CH3OCH2-OR)羥基保護(hù)示例(J. Org. Chem. 1995,60,7796)
To a stirred solution of (1) (51.0 g, 99 mmol) in CH2Cl2(1.0 L) at room temperature were successively added DIEA (51.5 mL, 0.297 mol) and MOMCl (15.0mL, 0.198 mol) over a 10 min period. Thesolution was stirred 11 h at room temperature after which a saturated aqueousNH4Cl solution (200 mL) was added. The aqueous phase was segregated, and the organic one was washed withwater (100 mL), brine (100 mL0, dried with anhydrous MgSO4, filtered, andconcentrated to give pure MOM ether (2) (55.3 g, 100%) (slightly yellowish oil).
二、利用MOMCl上保護(hù)時(shí)，對(duì)于位阻較大的羥基，有時(shí)在反應(yīng)中會(huì)加入NaI促進(jìn)反應(yīng)。原位生成了MOMI增加了反應(yīng)活性。
三、CH2(OMe)2，DCM，TfOH，室溫4h，產(chǎn)率65%。【J. Org. Chem., 57, 940（1992）】此方法使用于生成伯、仲、烯丙基和炔丙基的MOM醚。叔醇不能完全反應(yīng)，1,3-二醇則生成亞甲基縮醛。
利用甲醛二甲縮醛上MOM的方法中，還有其他酸性催化的方法，如TsOH/LiBr，無水三氯化鐵，五氧化二磷等等。
脫保護(hù)條件：
一、少量濃鹽酸，甲醇，62℃，15min。
二、6M HCl， THF/H2O，50℃，5-8h。
三、少量濃鹽酸，異丙醇，加熱。
To a stirred solution (1) (1.00 g, 1.45 mmol) in dry isopropylalcohol (10.0 mL) were added two drops (~0.06 mL) of concentrated aqueous hydrochloric acid. The solution was stirred at 55oC for 10 h and although incomplete as indicated by TLC analysis, was allowed to cool to room temperature (prolonged reaction timestend to give substantial decomposition). A saturated aqueous NaHCO3 (20 mL) and diethyl ether (50 mL)were added to the mixture. The phase wasseparated and the aqueous layer was extracted with diethyl ether (5 ′ 50 mL). The combined organic layer was washed with brine (10 mL), dried over MgSO4, filtered, and concentrated. The crude product was purified by flashchromatography to give (2) (0.63 g, 65%).
四、苯硫酚，三氟化硼乙醚，98%產(chǎn)率。【J. Am. Chem. Soc., 100，1938(1978)】
五、PPTS（對(duì)甲苯磺酸吡啶鹽），叔丁醇，回流80-90%產(chǎn)率?！?em>Synth. Commun., 13, 1021（1983）】
六、三氟乙酸，二氯甲烷，產(chǎn)率85%?！?/span>J. Am. Chem. Soc., 103，3210(1981)】
