Under the crab-apple trees they dipped and whispered, a Greek tycoon here, an Italian arts patron there, an expensive woman in the springtime breeze. Renoir should have painted it.

"Ahhhhhhhhhh," said American collector Arthur Altschul to Michael Jaffe, a Cambridge professor who came in black tuxedo and distinquished gray hair. "Art brings us together." They nodded elegantly, murmured several more "Ahhhhhhhhhhs," then spoke of global art.

"But where did we meet?" said Altschul.

"Near Oxford," replied Jaffe. "We shared a bathroom."

"Ahhhhhhhhhh," said Altschul.

This conversation was occuring on the seventh-floor outdoor terrace of the National Gallery of Art loaded with 250 people who came to drink, eat and then preview the exhibit "Post-Impressionism: Cross Currents in European and American Painting, 1880-1906."

Despite all the hoopla and fine twittering, the show is nonetheless a stand-in that National Gallery Director J. Carter Brown threw together after the Russian invaded Afghanistan and presidential policy forced the cancellation of the Hermitage exhibit from Leningrad.

Still, Brown was cooing last night. He got the exhibit this winter from the Royal Academy in London, and got also most of those paintings he'd rated as 10, as in zero to 10.

And as in Bo Derek?

"Heh, heh, heh, heh," Brown said. "Why not? I think there are a variety of qualities you look for -- and in the Gauguin, it's sexiness."

More than 170 public and private donors lent works to the show, but last night, the most exotic of them might have been two Greek shipping families who had cocktails only feet apart and insisted all those stories about feuding tycoons were so much twaddle.

"It's a big myth," said Philip Niarchos, son of Stavros, the Greek meganagnate. "If you want to know a big secret, we have dinner quite often."

The second half of the "we" was in fact Basil Goulandris, the other Greek tycoon on the premises, who has loaned Gauguin's "Sunflowers and Apples" to the exhibit. Normally it hangs in the dining room of his Gstaad, Switzerland, chalet, one of a host of homes he seems to have lost count of.

"It's very complicated," he said. "Better not to mention any numbers." On art, he was considerably less muddled.

"I consider the art collection part of the joie de vivre," he said. "You see?" Mais oui.

Meanwhile, a crab-apple tree and a half away, son-of-tycoon Niarchos was denying that his father had bought the $5.2 million Van Gogh sold in New York last week. "Some stupid London dealer went around spreading that rumor," said Philip Niarchos. "I can categorically say he did not buy it."

In addition to the Portuguese, Italian and Greek ambassadors, Americans and Greek ambassadors, Americans like Sen. Alan Simpson (R-Wyo.) the Averell Harrimans, the Livingston Biddles and architect I. M. Pei made it to the dinner. All the women wore long, sparking gowns.

One, however, was preoccupied with her bodice. She kept tugging at it.

"If my top slips down," said Lori Zelenko, arts editor of L'Officiel U.S.A. magazine, "I'll be a Gauguin. By the end of the evening I'll be a Renoir."