Marriott Corp. yesterday raised its offer to buy back a huge block of its stock by $1.50 a share and announced it has completed a deal to sell six of its hotel buildings for $159 million.

Both moves apparently are part of a major restructuring of Marriott's corporate financial structure. Details of the company's strategy are expected to be disclosed in a formal offering that is to be issued today.

Marriott said it would pay $23.50 per share for up to 10.6 million shares of its common stock -- more than one-third of the outstanding shares and nearly 40 percent of the stock that is not owned by members of the Marriott family.

The stock buy-buy will cost the corporation about $250 million, including a 25 cents per share payment to stockbrokers whose clients accept the offer.

Only a week ago Marriott stunned investors when it announced it would buy back its stock at $22 a share. The company said it would purchase at least 5 million shares and perhaps up to 11 million, depending on the outcome of negotiations to sell some of its hotel properites.

With the completion of the hotel sale, to Equitable Life Assurance Society of the U.S., Marriott raised the price of its offer and aimed for the maximum number of shares.

After the first announcement Marriott shares which had been trading on the New York Stock Exchange for less than $20, immediately jumped to $22 a share. Yesterday's announcement made the stock jump again, to 23 7/8.

The simultaneous purchase of stock and sale of hotels reflect a move by Marriott to reduce its capital needs and rebuild its financial base, Wall Street analysts who follow the company said yesterday.

The moves will increase Marriott's earnings per share of stock dramatically and will sharply boost the company's return on its invested capital.

Improved return on equity has been a key corporate goal of Marriott for several years. It's not that current performance is bad analysts emphasized, it's that the new generation of Marriotts now running the company thinks it could be even better.

Two years ago the company began selling some of the hotel properties it owned and said its plan was to manage hotels owned by other investors.

Marriott said it would rather let other investors put their money into hotel real estate and earn its profits by operating the businesses. That strategy sharply reduced Marriott's need for capital to expand, because hotel and restaurant operations require relatively small cash investments.

The latest hotel sale will free up additional cash, which will be used to reduce the company's debts or to buy back shares.

The hotel properties Marriott is selling include the Tan-Tar-A resort at Lake of the Ozarks, Mo., the Marriott Hotel in downtown Atlanta, and the Rancho Las Palmas resort near Palm Springs, Calif. Also included in the package are three hotels that are still being built, at Anaheim, Calif., Westchester County, N.Y., and Nashville, Tenn. All the hotels will continue to be managed by Marriott and run under the Marriott name, but the insurance company will own the buildings and rent them to Marriott.