Installing package in Linux CentOS

I've followed the instruction on this page
http://www.couchbase.com/develop/c/current

For the First one
[couchbase]
name = Couchbase package repository
baseurl = http://packages.couchbase.com/rpm/5.5/i386

I've installed successfully

For ths Second one,
[couchbase]
name = Couchbase package repository
baseurl = http://packages.couchbase.com/rpm/5.5/x86_64

[root@peach ~]# sudo yum install libcouchbase-devel
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: data.nicehosting.co.kr
* extras: data.nicehosting.co.kr
* updates: data.nicehosting.co.kr
Setting up Install Process
No package libcouchbase-devel available.
Nothing to do
[root@peach ~]#

Whats wrong with it?
Can anyone explain how to install library on Linux CentOS?