- A+
MOM（甲氧基甲基醚）是一种保护羟基的常用方法；其对酸还是较为稳定的，一般它的脱除需要在强酸条件下进行。
保护条件：
一、CH3OCH2Cl（MOMCl），DIEA，在二氯甲烷中，0℃到室温，反应8h，在引入MOM时，此条件是最常用的方法。但是MOMCl是致癌物，而且在制备MOMCl时产生的二氯甲基甲基醚毒性更强。因此在使用MOMCl时要做好防护措施。
MOM(CH3OCH2-OR)羟基保护示例(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上保护时，对于位阻较大的羟基，有时在反应中会加入NaI促进反应。原位生成了MOMI增加了反应活性。
三、CH2(OMe)2，DCM，TfOH，室温4h，产率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。叔醇不能完全反应，1,3-二醇则生成亚甲基缩醛。
利用甲醛二甲缩醛上MOM的方法中，还有其他酸性催化的方法，如TsOH/LiBr，无水三氯化铁，五氧化二磷等等。
脱保护条件：
一、少量浓盐酸，甲醇，62℃，15min。
二、6M HCl， THF/H2O，50℃，5-8h。
三、少量浓盐酸，异丙醇，加热。
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%产率。【J. Am. Chem. Soc., 100，1938(1978)】
五、PPTS（对甲苯磺酸吡啶盐），叔丁醇，回流80-90%产率。【Synth. Commun., 13, 1021（1983）】
六、三氟乙酸，二氯甲烷，产率85%。【J. Am. Chem. Soc., 103，3210(1981)】
Aromatase inhibitor-associated bone loss and its management with bisphosphonates in patients with breast cancer. tamoxifen pill
Gujarat s government has invested heavily in roads, ports, agriculture and power, creating visible signs of progress in contrast to other parts of India levitra dosage belgique Vitek; University Hospital, Prague J
You actually make it seem really easy with your presentation however I in finding this topic to be actually something
which I believe I would by no means understand. It kind of feels too
complicated and very wide for me. I'm looking forward on your subsequent put up, I will attempt to
get the dangle of it!
Have a look at my web blog ... how to buy cialis
Filing a Stevens Johnson Syndrome lawsuit may help you obtain compensation for medical bills, pain and suffering and other damages priligy online pharmacy 0 agreed that not having enough time to provide breast cancer health promotion to patients visiting the pharmacy, 124 62
That is a really good tip particularly to those fresh to the blogosphere.
Brief but very precise info_ Thank you for
sharing this one. A must read post!
casino en ligne francais
Greetings from Ohio! I'm bored to tears at work so I decided to check out your
blog on my iphone during lunch break. I enjoy the information you present here and can't wait
to take a look when I get home. I'm surprised at how
quick your blog loaded on my phone .. I'm not even using WIFI, just 3G ..
Anyhow, superb blog!
casino en ligne
Great beat ! I would like to apprentice whilst you amend your web
site, how could i subscribe for a blog web site? The account
aided me a applicable deal. I have been a little bit familiar of this your broadcast offered brilliant clear concept
casino en ligne
Hey just wanted to give you a quick heads up. The text in your article seem to be running off the screen in Chrome.
I'm not sure if this is a formatting issue or something to
do with web browser compatibility but I thought I'd post to
let you know. The style and design look great though! Hope you get the problem solved soon. Thanks
casino en ligne francais
We're a group of volunteers and opening a new scheme in our community.
Your site provided us with valuable info to work on. You've done an impressive job
and our whole community will be thankful to you.
casino en ligne
Asking questions are really fastidious thing if you are not
understanding something fully, however this post
provides nice understanding yet.
casino en ligne
I think this is one of the most important information for me.
And i'm glad reading your article. But should remark on few general things, The web
site style is great, the articles is really nice : D.
Good job, cheers
casino en ligne
It's actually very complicated in this busy life to listen news on TV, therefore I just use the web for that reason, and get the newest information.
casino en ligne francais
Hello there! This is my first visit to your blog!
We are a group of volunteers and starting a new project in a community in the same niche.
Your blog provided us valuable information to work on. You have done a
outstanding job!
casino en ligne
It's impressive that you are getting ideas from this post as well as from our dialogue made at this time.
casino en ligne