NEW YORK CITY-SecondMarket Holdings, Inc. has leased 50,000 square feet at 636 Avenue of the Americas, making the provider of alternative investments the building’s anchor tenant.

The building was the first property bought by Billy Macklowe, CEO of William Macklowe Co., after leaving his father’s firm last year. It was purchased with Clarion Partners--then ING Clarion Partners--for $45.2 million.

SecondMarket will occupy floors three through six as well as the penthouse, in a move from 26 Broadway anticipated to take place in early 2012. Matthew Astrachan, a Jones Lang LaSalle vice chairman who represented the William Macklowe Co. and Clarion Partners in the lease, tells GlobeSt.com that the new tenant will also have signage in the lobby and some branding on the outside of the building as well.