Sunstone Hotel Investors, an Aliso Viejo, Calif.-based lodging real estate investment trust, or REIT, said on Thursday that it has agreed to buy the 544-room Wailea Beach Marriott Resort & Spa in Maui for a net purchase price of $325.7 million from an affiliate of Blackstone Group LP.

The fee-simple property is on 22 waterfront acres on Wailea Beach Marriott adjacent to the Shops at Wailea.

The transaction is expected to close in the third quarter, Sunstone said.

Sunstone said it will invest about $65 million into upgrading the hotel in 2015 and 2016, focused primarily on public areas. The company said the upgrades will allow it to increase the average daily room rates at the hotel.

The purchase is the first in Hawaii for Sunstone, which owns an interest in 29 hotels with 13,740 rooms in the "upper-upscale segment," according to its website.