The 31-year-old Astana rider prevailed in a sprint battle for the line with Ukraine's Andriy Grivko, an Astana team mate, taking silver and Czech Petr Vakoc bronze.
Another Spaniard, Jesus Herrada, was fourth after providing sterling assistance to Sanchez, who claimed a bronze medal in the individual time trial on Thursday.
Sanchez knew he had victory in the bag metres before the finish line at Freedom Square, sitting up and raising both hands in triumph at the end of the 215.8 km race around the streets of the capital.
Sanchez and Herrada, who gave his team mate a perfect lead-out and allowed him to launch his powerful surge 100 metres from the finish that Grivko and Vakoc were unable to counter, shared an emotional embrace.
"I told him this medal was for him, and for the team," Sanchez told reporters.
"I know him from sharing rooms, not only this week but from the world championships and he's a great team mate and a promising rider."
Early in his career, such was Sanchez's prodigious talent he was compared to Spanish great and five-times Tour de France winner Miguel Indurain.
He won the 2005 Tour Down Under but his career stalled following his biggest triumph in winning the Paris-Nice in 2009, despite adding Tour de France stage wins in 2011 and 2012 to successes in 2008 and 2009.
In 2013, Team Pro Blanco cycling, formerly Rabobank, provisionally suspended Sanchez, who has always denied doping, over accusations he was linked to Spanish doctor Eufemiano Fuentes in the Operation Puerto blood doping racket.
He was reinstated a few weeks later but was then let go by the Belkin team (previously Pro Blanco) over continued speculation.
After one season with second-tier Spanish team Caja Rural Sanchez was signed at the start of 2015 by Astana on a one-year deal.
"When you start losing confidence in yourself it's hard, but I kept going, working hard and training a lot, step by step and waiting for the precise moment," he said.
Asked if the doping allegations were now long behind him, Sanchez replied: "I keep doing my job, for myself, for my family, for the benefit of my team and for my national team."
(Reporting by Justin Palmer, editing by Pritha Sarkar)
Share
