Hans Gildemeister, 22, and Patricio Cornejo, 34, two friends from Santiago, Chile, put their friendship aside for 1 1/2 hours yesterday on the clay courts at 16th and Kennedy streets NW and Gildemeister used his two-handed forehand and youth to come from behind and post a 3-6, 6-2, 6-2 win over Cornejo in first-round play in the Washington Star International tennis cahampionships.

The short dark-haired Cornejo opened up the first set winning the first two games easily over blond, long-haired Gildemeister. But his younger foe bounced right back to make the first set 2-all. Mirroring that, Cornejo won the next two games; Gildemeister broke Cornejo's service in the seventh game, but the elder Chilean broke right back and held service to win the first set.%TGuildemeister recovered and the second set saw his forehand at its best.

He hit the ball deeper and harder to win the first three games and coasted to take the set.

Guildemeister did not seem to tire in the third set, but his veteran opponent slowed considerably. Again Gildemeister opened the set by winning three straight games and wrapped up the match.

Coming off the court after his defeat, Cornejo said, "I was lost. If I could have broken in the first game of the second set then I probably would have won. But he got a jump on me. His backhand was great and he was too fast on the court."

Guildemeister's victory put him into a second-round match against Peter Fleming, who won his match today against Canadian Greg Halder, 6-1, 7-5.

In th only upset of the afternoon, Larry Gottfried, younger brother of Brian Gottfried, was ousted by Ivan Molina of Columbia, 6-3, 6-1.

Also in afternoon play, Terry Rocavert of Australia beat Peter Pearson San Francisco, 6-3, 6-1; Bill Scanlon of Dallas suffered a defeat at the hands of Paraguay's Victor Pecci, 6-1, 6-4, and Bolivia's Ramiro Benavides defeated Mexico's Marceki Kara, 7-5, 6-4.

Afternoon matches today will pair Mexico's Raul Ramirez against Billy Martin, and Arthur Ashe, the only player to have entered all the Star tournaments, against Junior Davis Cup player Robert Van't Hof. Van't Holf, 19, is in the Star tournament for the first time.

The evening matches will begin at 7 o'clock with Manuel Orantes of Spain challenging France's Christophe Freyss. Orantes, a left-hander, is ranked seventh in the world.

The Washington Area Tennis Patrons will celebrate Ken Rosewall night. Rosewall will be featured in the evening's second match against John James.

Matches begin at noon with contests on four courts.