According to boxkite:

USA:
* Douglas project (shaft drive). This company is developing a fifty-passenger helicopter as a DC-3 replacement type. Engines may be two Rolls-Royce RB 109 turboprop variants. [I believe this is either the patent shown here ->http://www.secretprojects.co.uk/forum/index.php/topic,898.msg20402.html#msg20402 (too early), nor the compound helicopter from AIR PROGRESS - Spring 1962, page 40 (too late).]