NEW YORK — Scott Greenstein, senior vice president of motion pictures, music, new media and publishing at Miramax Films, is leaving the specialized film powerhouse, sources said Wednesday.Greenstein is often referred to as the “third Weinstein brother” because he has the ear of Miramax co-chairmen Bob and Harvey Weinstein. Nevertheless, he has informed them he will not be renewing his contract when it expires shortly. Miramax, a unit of the Walt Disney Co., could not be reached for comment. Sources close to Greenstein believe the only reason he would resign would be to play a leadership role at another company. They said his relationship with the Weinsteins remains close. Rumors were circulating that Greenstein would be joining October Films as co-president, but the arthouse distrib already has three co-managing directors — Amir Malin, Bingham Ray and John Schmidt. A source close to October did not deny that Greenstein had been offered a senior position by the company, in which Universal Pictures recently acquired a majority interest. He noted that Greenstein is also being wooed by 20th Century Fox. The source pointed out that as long as Greenstein is under contract at Miramax, he cannot accept a new job. An attorney, Greenstein joined Miramax in 1993 as VP, motion pictures, music and new media. Before that, he was VP-counsel for Viacom Intl. At Miramax, he has played a key role in negotiating film and music contracts, including the acquisition of Billy Bob Thornton’s “Sling Blade.” Greenstein represented Miramax after the Weinsteins decided to step in and produce Anthony Minghella’s “The English Patient,” and helped negotiate Minghella’s agreement to direct his upcoming “Cigarettes and Chocolate” for Miramax. Greenstein follows several key Miramax execs in his decision not to renew his contract. Among those who have recently ankled are exec VP of production and acquisitions Trea Hoving, exec veepee of business and legal affairs John Logigian, senior VP of communications Donna Daniels and senior veep of acquisitions Eamonn Bowles.