Dear Anatoly Fedorov ,

It looks quite similar to the Baylis-Hillman reaction. But, instead of a tertiary amine or phosphine, it is the OH group (blue) the one that gives the nucleophilic addition to the beta position (red). This is followed by intramolecular enolate trapping (red alpha carbon to blue carbonyl to form the final adduct. And, unlike Baylis-Hillman reaction, this process does not regenerate the initial enone upon deamination/dephosphination, so it keeps the furan moiety.

Hope you find it helpful

Dear Enrique Manuel Arpa ,

Thank you for your clear and exhaustive answer. It helped quite a lot.