Arsenal's attempt to strengthen their midfield have been frustrated after Bayer Leverkusen knocked back an approach for the Germany international Lars Bender. The club have, however, signed the French French youth international striker Yaya Sanogo as a free agent after leaving Ligue 2 team Auxerre.

The Gunners had hoped to secure the 24-year-old, whose twin brother Sven plays at Borussia Dortmund, for about €23m (£18.5m) but the Bundesliga club quickly turned down the inquiry and have since made it clear Bender is not for sale at any price. Leverkusen sold André Schürrle to Chelsea and Dani Carvajal to Real Madrid earlier in the summer and are not under financial pressure to move on more of their first-team squad.

That represents a blow for Arsène Wenger, whose transfer policy this close season has always been geared towards strengthening the spine of his side with a striker, a central midfielder and an experienced goalkeeper his priorities.

Real's Gonzalo Higuaín is set to join for £22m up front while a deal for Queens Park Rangers' Júlio César, the Brazil No1, for around £1.5m is also close, but other options will now have to be pursued in midfield. A late attempt to secure the France international Etienne Capoue from Toulouse failed on transfer deadline day in January, and Wenger remains interested in Dortmund's Ilkay Gündogan and the Everton midfielder Marouane Fellaini.

Arsenal are understood to be reluctant to meet the £24m release clause – which applies to Champions League clubs and expires in mid-August – in the Belgian's contract, and the Merseysiders are in no rush to sell Fellaini.

Arsenal have succeeded in loaning their Switzerland defender Johan Djourou to Hamburg on a 12-month arrangement while the third-choice goalkeeper, Vito Mannone, has joined Sunderland for a fee of around £2m.

Sanogo joins on a long-term deal having made 24 first team appearances for Auxerre and scoring 11 goals.