The Boston branch of law firm Skadden, Arps, Slate, Meagher & Flom will vacate its One Beacon St. offices next March, opting instead for the amenity-rich Back Bay.

The law firm, based in New York City, will move its Boston operations to 500 Boylston St. and occupy 47,000 square feet of office space on floors 21 and 22, according to a company spokesperson.

"We are delighted to welcome Skadden to 500 Boylston St., one of our premiere Class A buildings in the Back Bay," Ryan Enright, vice president of leasing for Equity Office, which owns the 25-story property, said in a prepared statement.

This is the first sizable lease Equity has executed at the property since MFS announced it would vacate 350,000 square feet in the upper floors of 500 Boylston, which contains about 715,000 square feet of total rentable space, according to real estate executives that asked for anonymity.

Skadden, which occupies more than 60,000 square feet of space at One Beacon St., is significantly shrinking its footprint, a move that has become more common in the legal industry. Law firms have little need for the massive libraries that most firms have kept on-hand for so long since the information can instead be contained online. And many firms are learning to live without a secretary for every partner.

"The [contraction] is the result of a combination of things; the location, the building itself, and it’s probably more convenient to employee housing and for partner access, many who probably live west of the city," said Barry Hynes, senior managing director for the Boston office of commercial brokerage firm Cassidy Turley. "The industry is changing so much today with a lot being done electronically. And the Back Bay has a lot of cache, there’s no doubt about it."