Pierre-Emerick Aubameyang saw a last-minute penalty saved by Hugo Lloris to cost Arsenal victory and ensure Tottenham retained a crucial advantage over their arch-rivals in the battle for a top four place after a dramatic north London derby at Wembley.Harry Kane's contested penalty put Spurs level with 16 minutes left after Aaron Ramsey's coolly-taken 16th-minute goal threatened to inflict a third successive league defeat on boss Mauricio Pochettino for the first time in his reign.Arsenal were then handed a golden opportunity to close to within one point of Spurs after Davinson Sanchez fouled Aubameyang but the striker's tame penalty was easily saved low to his right by the diving Lloris.And to add to the late chaos, Arsenal's Lucas Torreira was sent off for a reckless challenge on Danny Rose in the closing seconds.After Ramsey's strike, keeper Bernd Leno kept Arsenal on level terms with a miraculous double save from Christian Eriksen and Moussa Sissoko but the Gunners paid a heavy price for a glaring second-half miss from striker Alexandre Lacazette before Aubamayeng's wayward spot-kick.Lacazette failed to hit the target from eight yards and Spurs took advantage, Kane scoring from the spot to equalise after referee Anthony Taylor adjudged he was fouled by Shkodran Mustafi.Arsenal were also angry as they believed offside should have been given in the build-up but Kane stayed calm amid the chaos to send Leno the wrong way from the spot for his ninth goal in this fixture and keep Spurs four points ahead of Unai Emery's side.The Gunners, however, have only themselves to blame after spurning that late chance to seal a league double over Spurs.