When I was an undergraduate, learning all the chemical reactions that you have to learn in undergraduate courses, I got a few wrong ideas into my head. Well, probably more than a few, but you know what I mean.

One of them came from Theodora Greene's book on protecting group chemistry, which was a new item in its first edition around the time I was doing my first summer research project. This was, and remains, the best single source for finding out how to attach and remove groups that will protect reactive parts of your molecule until they're ready to be unveiled. Organic chemists spend a fair amount of time using these, especially for things like amines and hydroxyl groups, which are liable to become personally involved in all sorts of reactions if they're not restrained.

In my first encounters with these, I got the (completely mistaken) impression that all protecting groups tended to have specific recipes, precisely targeted for their removal. Methoxymethyl ether group to take off? Reach for the zinc bromide! Pivaloyl ester? Methyllithium! And so on. There was page after page of this sort of thing.

And it's not like those are poor choices, to be sure. I've used that methyllithium one myself, although not since about 1988. But zinc bromide isn't called for because of its essential zinc bromidey properties, it's called for because it's a Lewis acid, and just about any Lewis acid will take off a MOM group. Some will be faster than others, some might do things to the rest of your molecule which others wouldn't, but they'll all get around to cleaving your methoxymethyl ether. As will good old protic acids - aqueous hydrochloric will take one off just like it was 1895 again, if the rest of your molecule can stand it.

Learning all this, which I did in my later undergraduate years, was a good way to start appreciating the mechanistic side of organic chemistry. There really aren't that many reactions, no matter what poor sophomores think while they memorize page after page of them. Organic chemistry isn't zoology. And it also hit me, after a while in graduate school, that the claim of a new, mild, wonderful way to remove a given protecting group was a pretty good method to get a paper published, which might - just might - have something to do with their proliferation.