Just go to the iTerms2 preferences -> Profiles -> Keys -> set the Left/Right Option key to Esc+.
;; Enable mouse support
(unless window-system
(require 'mouse)
(xterm-mouse-mode t)
(global-set-key mouse-4 » (lambda () (interactive) (scroll-down 1)))
(global-set-key mouse-5 » (lambda () (interactive) (scroll-up 1)))
(defun track-mouse (e))
(setq mouse-sel-mode t))