The 15-year-old boy was attacked on a footpath next to Bogston Railway Station at 9.30pm.
The boy managed to defend himself but suffered minor injuries.
The culprit fled empty handed.
Police are treating the incident as an assault with intent to rob and officers have issued a description of the man.
He is 5ft 7’ tall with dark hair and a fringe.
He was wearing a bright orange top and jogging bottoms.
Detective Constable Sharon Crawford, of Greenock CID, is appealing for witnesses and says the man may have been hurt in the incident.
She said: “The suspect may have been injured.” Anyone with information should call police on 101.
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