The exhibition "21 Rue La Boétie" is on display at Paris Musée Maillol until 23 July 2017. The name of the exhibition is not simply an allusion to a landmark Parisian address of the gallery, and exposition of the artworks by painters like Picasso, Ensor and Toulouse-Lautrec, but also the significant insight into the human history connected with nazism.
Main hero of the show is Paul Rosenberg. He was born in 1881 in a family of an antiquarian. Altogether with his brother Léonce, the Parisian has began to settle the art deals since his youth. In a while, brothers opened their own separate galleries according to their preferences in art. Léonce remained faithful to his passion for the Cubism, a lead that Paul followed as well, but eventually Paul switched to Modernism. 

Paul Rosenberg in the gallery, 1914, © Archives Paul Rosenberg & Co, New York

Мари Лорансен. Репетиция
Мари Лорансен

Although it sounds cynical, the World War I played an important positive role in Paul's life. Daniel-Henry Kahnweiler, the art dealer who was "in charge" of artworks by Picasso, was forced to leave France due to his German origin. So Paul became a new art dealer for Pablo.
Pablo Picasso, Portrait de Madame Rosenberg et sa fille (Portrait of Mrs. Rosenberg and Her Daughter), 1918. Musée Picasso, Paris
© Succession Picasso 2016 © RMN — Grand Palais musée Picasso de Paris — © Thierry Le Mage

Rosenberg was also a friend and agent of Henri Matisse, Georges Braque, Fernand Léger, Marie Laurencin – the famous cohort of renowned artist. On 1940, the collection comprises of several hundreds of artworks: both canvases and sculpture.

World War II, on the contrary, destroyed life of Rosenberg. It's easy to guess that his family name was not of a representative of the titular nation. Everyone knows what Jews could receive under the Nazi occupation. Saving his life, Rosenberg left part of the collection, including the most heavy samples (for example, sculptures of Auguste Rodin and Aristide Maillol), and tried to take out at least the most valuable paintings of Picasso, Matisse, Braque.

Жорж Брак. Лежащая обнаженная
Лежащая обнаженная
Жорж Брак
Альфред Сислей. Дорога в Версаль
Дорога в Версаль
Альфред Сислей
1875, 47×38 см
Exhibition of the artworks by masters of nineteenth century in the 21 Rue La Boétie gallery 
(©Archives Paul Rosenberg & Co, New York)

Анри Матисс. Фортепиано
Анри Матисс
Now that we have knowledge about events of those years, Paul's attempt seems naive to us, but then people did not realize the scale of the tragedy that had come to France. The art dealer handed over four hundred canvases to store in a bank. Of course, the masterpieces were confiscated. Their new owners were Reichsmarschall Hermann Goering and German Foreign Minister Joachim von Ribbentrop...

The gallery at a landmark Parisian address was turned into a center of anti-Semitic propaganda. Since may 1941 there was a so-called Institute for the Study of the Jewish Question.

Fortunately, Rosenberg and his family managed to expatriate with a small part of the collection to the USA via Portugal, where they started a new page of their life, definitely connected with the arts. Art dealer died in 1959. As time went, his descendants started gathering paintings stolen by the Nazi from the Rosenberg's gallery all around the world.

Мишель Мишель-Жорж -Жорж. Открытие балета "Парад" в Париже. (Поль Розенберг, Мари Лорансен, Сергей Дягилев, Мисия Серт, Эрик Сати,  Жорж-Мишель, Пикассо, Жан Кокто)
Открытие балета "Парад" в Париже. (Поль Розенберг, Мари Лорансен, Сергей Дягилев, Мисия Серт, Эрик Сати, Жорж-Мишель, Пикассо, Жан Кокто)
Мишель Мишель-Жорж -Жорж
1917, 45.8×35.7 см

1.1. Pablo Picasso, Mademoiselle Rosenberg 1919 © Succession Picasso 2016
1.2. Pablo Picasso, Portrait of Paul Rosenberg 1918-1919 © Succession Picasso 2016 © Photo: Studio Sebert / Galerie Troubetzkoy
For example, one of the pictures, Woman Sitting in a Chair by Henri Matisse (1921) was discovered in a scandalous Gurlitt collection and has already been returned to the family of the original owners.

The painting “Woman in Blue in Front of Fireplace” by Matisse occurred in 2012 when it was on loan to the Pompidou Center in Paris. There, the picture attracted attention of the experts who knew its story: “Woman in Blue in Front of Fireplace” was among the paintings taken by Hermann Goering. After the war, the work was bought by Henie Onstad, a collector from Norway, and kept in the Henie Onstad Arts Center in the suburbs of Oslo.

This museum (unlike others) did not compete too fiercely for the disputed property, and it costed no long-standing litigation. So, in 2014, the canvas returned to the family of Paul Rosenberg's descendants.

The book of Anne Sinclair, the granddaughter of the art-dealer, is devoted to the peripeteias of his life, relations with artists and fate of the collection in the complicated epoch. The author herself is a well-known person: a French political journalist, the ex-wife of the former International Monetary Fund managing director Dominique Strauss-Kahn, who abruptly left the institution following allegations of sexual assault in 2011, but it is a completely different story.

Sinclair's book is entitled the same as the exhibition. Rather, the display is based on the book. The exhibition was previously shown at the Musée de La Boverie de Liège (Belgium), from where it moved to Paris.

(This and the photo bellow from the exhibition depicting work of James Ensor -

The exhibition brings together some sixty canvases. "Many of the artworks on display have a direct connection to the dealer, having been shown in his galleries in Paris or New York, while others provide a significant insight into the historical and artistic context of the time." Visitors can also view photographic portraits of the art dealer and photo shots presenting the 21 Rue La Boétie gallery's interiors. 

Masterpieces came from different museums (including the Centre Pompidou, the Musée d’Orsay, the Musée Picasso in Paris but not only; you can see the whole list at the end of the exhibition video ad) and from private art collections in Europe.
Анри де Тулуз-Лотрек. Жюстин Диель в саду Фореста
Жюстин Диель в саду Фореста
Анри де Тулуз-Лотрек
1890, 74×58 см

This exhibition is mentioned as "a real event in the European cultural life," and there are lines in its press release calling his main hero "one of the most influential art dealers in the first half of the twentieth century," and "an avid art collector, astute businessman and discerning amateur, friend and agent to some of the biggest artists of his day."

Asia Rysevich. Article is written on materials of the exhibition official website, articles of Archive and  art-and-houses.