"We don't have any walls," said Ray Millora, the Glaxo project manager for the move.
No walls means no art on walls.
Glaxo officials decided to sell works at a substantial discount to employees and to put the rest up for auction, with the notable exception of the Wyeth.
Robert W. Carr, GSK senior vice president for environment, health and safety, said proceeds from the sales will go to local charities.
Painted in 1929, the Wyeth depicts a dramatic moment in Homer's Odyssey. A powerful Odysseus has returned home from decades of war and wandering and is about to shoot an arrow from his mammoth old bow through a tunnel formed by a series of curved ax heads. A crowd of assorted interlopers and moochers looks on, interested, but so far unaware that that the bow will be turned on them.
"This is a moment of revelation," said Kathleen Foster, the museum's curator of American art. "It takes genius to seize the right moment" in a story, she said, referring to Wyeth's prolific career as a highly sought-after illustrator. "He was so good at that."
The painting, The Trial of the Bow, is one of 16 made by Wyeth to accompany a new edition of Homer. The entire Odyssey series was sold by the artist - who lived in Chadds Ford with his family, including his son, painter Andrew Wyeth - to a private collector in 1930.
The paintings were subsequently scattered and most have yet to be located. A huge trove of Wyeth family art is held by the Brandywine Museum in Chadd's Ford, a fact that has served to attract even more Wyeths to that institution, said Foster. The Philadelphia museum has hardly had a chance to get its foot in the door, she said.
Glaxo acquired The Trial of the Bow in the 1980s, said Millora, amid circumstances that are unclear.
In addition to the Wyeth, the museum also announced several other gifts, including four 18th- century paintings currently in the exhibition "Journeys to New Worlds: Spanish and Portuguese Colonial Art from the Roberta and Richard Huber Collection," on view in the Perelman building.
The paintings include King Luis I of Spain on Horseback, from Peru; Saint Anthony of Padua Preaching Before Pope Gregory IX, also from Peru; The House at Nazareth, from Bolivia; and Our Lady of the Reedbed of Irún with Donor, Captain Joaquín Elorrieta painted by Ecuadorian artist José Cortés de Alcocer.
The museum also acquired Redouté's Amaryllis Josephine, a double-page watercolor on vellum, accompanied by a pencil drawing of the flower bulb; and a stained-glass and bronze chandelier made about 1905 by Tiffany Studios.
More than 220 images by American photographer Paul Strand were acquired at the end of 2012.
Timothy Rub, museum director, noted that more than 90 percent of the museum's approximately 227,000 artworks entered the collection by donation, a fact that the recent acquisitions underscores.
Contact culture writer Stephan Salisbury at 215-854-5594, firstname.lastname@example.org, or @SPSalisbury on Twitter