JERUSALEM — An award-winning professor at the Hebrew University of Jerusalem, Raphael Mechoulam is a trim gentleman who wears tweed jackets and silk scarves. Despite the respectability, Mechoulam's greatest fame stems from science that may earn him a warm welcome among cannabis proponents. He was the first person to synthesize THC, the principal active ingredient in weed. That leap is what has enabled the drug to be studied scientifically. And at 82, Mechoulam is still making an impact; Before CNN's Sanjay Gupta made his famous about-face on medical marijuana this month, the TV physician visited the Israeli's lab.