Change the Option+R/L shortcuts to Control+R/L
In the first example below Option-L/R arrow does the same after adjusting the keycodes as Control-L/R arrow.

The previous behavior Option-L/R arrow (e.g opening/closing a folder in list view) is lost.

If you want a different behavior you have to modify/precise your answer.

To make this work you have to use a third party tool: Karabiner.


Download, install and open Karabiner
Open in the menulet Karabiner -> Preferences
Open the tab Misc &amp; Uninstall
Hit the button Open private.xml
Open the file private.xml with an appropriate editor
Enter the customized keycode

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
      &lt;name&gt;Change Option L/R arrow to Control L/R arrow&lt;/name&gt;
      &lt;identifier&gt;altlr2ctrllr&lt;/identifier&gt;
      &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;
      &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;

Save the file
Open in the menulet Karabiner -> Preferences the tab Change Key
Hit the ReloadXML button
Enable the remapping. It should be listed at the beginning.




And if you are really asking for "Option+L/R shortcut on my Mac keyboard to Control+R/L" - which can be read as alt-l to ctrl-r and alt-r to ctrl-l in contrary to the headline - then use 

          &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;
          &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;




If you want the opposite (Control-L/R arrow does the same as Option-L/R arrow) use this snippet instead. The previous behavior of Control-L/R arrow is lost.

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;Change Control L/R arrow to Option L/R arrow&lt;/name&gt;
    &lt;identifier&gt;ctrllr2altlr&lt;/identifier&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION&lt;/autogen&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;




If you want to swap ctrl-L/R-arrow with ctrl-L/R-arrow then use either both of the above keycode changes or this one:

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;Swap Control L/R arrow and Option L/R arrow&lt;/name&gt;
    &lt;identifier&gt;swap_ctrllrarrow_altlrarrow&lt;/identifier&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL&lt;/autogen&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::CURSOR_LEFT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION&lt;/autogen&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::CURSOR_RIGHT, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;