Plans to build the seven-story Quartermile 4 and the five-story Quartermile 3 have now been finalised, with the former expected to be completed by 2016.
Together, the two blocks will offer almost 200,000 sq ft of office space with 12,490 sq ft of retail accommodation.
Paul Curran, managing director of Quartermile, said the project has already generated interest from potential tenants.
He added: "Construction of Quartermile 4 will commence in July this year making it the first speculative grade A office development to be undertaken in the city for a number of years.
"We are already seeing strong occupational interest and are working with our agents to secure lettings."
Quartermile is a mixed-use redevelopment based on the site of the former Royal Infirmary for Edinburgh.
It promises to provide a total of 320,000 sq ft of Grade A office space, along with more than 900 residential apartments.
The latest £80m in funding was agreed in a deal between owners Moorfield Real Estate Fund III and M&G Real Estate, the investment arm of insurer Prudential.
The project is expected to create between 300 and400 construction jobs.
John Fyfield, director of development at M&G Real Estate, said: "We are very pleased to have secured the final office phase of this very successful urban regeneration project off- market.
"At a time when there is a real lack of Grade A office space in Edinburgh the commitment to speculatively develop these buildings ensures they will be delivered into a market where there is little competition."
The entire Quartermile development is expected to be completed by 2018.