I tried the same command on my macBookPro and I can not reproduce the error you experienced:
sudo tar -zxvf couchbase-sync-gateway-enterprise_1.4.1-3_x86_64.tar.gz --directory /opt
The permissions on my /opt directory are:
drwxr-xr-x@ 7 root wheel 238 25 Apr 18:44 /opt
macOS version: 10.12.1
The user account that I am using to run the command has Admin privileges on my machine.
Andy