If you want to compile Bitcoin on CentOS 6, you will need more than just Bitcoin; several other dependencies are either missing or too old.
- Boost is too old. CentOS 6 has version 1.41, but Bitcoin requires features first introduced in Boost 1.47.
- Berkeley DB is too old. CentOS 6 has version 4.7, but Bitcoin wants version 4.8 (but see below for more on this).
- OpenSSL may be missing some elliptic curve algorithms required for Bitcoin, due to Red Hat's extremely conservative legal stance with respect to ECC. (See bugs 319901 and 1020292, among others.)
- The qrencode and miniupnpc libraries, necessary for the Bitcoin GUI to support QR codes and UPnP respectively, are missing entirely. (A server-only build doesn't need them, though.)
- Older versions of the Bitcoin codebase did not work with Qt 4.6, the version shipped with CentOS 6, but required Qt 4.7. I fixed this with a one-liner, and it was patched upstream. This probably won't affect you, though, unless you're building old code for some reason.
You also need these packages, which do exist in CentOS 6:
- autoconf automake libtool
And you also need this package from EPEL:
For a build including the GUI, you also need:
- qt-devel desktop-file-utils
Then you need to patch Bitcoin to accept using Berkeley DB 4.7; by default the configure script bails if BDB 4.8 is not present, even if you pass the configure option that is supposed to override this. And be warned that wallets created by this build may or may not work with Bitcoin compiled with BDB 4.8.
Then you need to patch it again to make it compile on the older versions of gcc and glibc shipped with EL6, as the current Bitcoin code assumes a compiler supporting C++11 is being used. It's a one line patch, but it took me half an hour to track down.
As you can see, this is kind of painful, and the missing libraries alone cause most people to give up.
Most of these packages (except miniupnpc) are in CentOS 7, so if you're going down this road, that's probably a better starting point.
I've been maintaining versions of those libraries, along with an SELinux-enhanced Bitcoin build, for a couple of years now. It's much easier to just grab the repo and install the existing RPM packages since I've done all this work for you. But if you really want to cover that ground again, there's your road map.