Lawyers for Mark Zuckerberg say he was extorted by Palo Alto developer in 2013 home purchase

In 2013, news broke that Facebook billionaire Mark Zuckerberg had bought four houses adjacent to his Palo Alto home.

Zuckerberg reportedly scooped up the four houses when he heard that a developer planned to build a large home on one of the lots behind his property.

But in May 2014, the developer, Mircea Voskerician, filed suit against Zuckerberg, claiming that the billionaire never followed through on an agreement they had made in secret.

In November 2012, Voskerician reportedly sent Zuckerberg a letter saying that he planned to tear down the home behind the Zuckerberg home and build a 9,600-square-foot mansion in its place. The new home, he said, would have a direct view of the Zuckerbergs' house, including their master bedroom.

A number of emails between Voskerician and Zuckerberg have been unearthed during litigation.

According to court filings reported on by Bloomberg, Voskerician then made Zuckerberg an offer that would preserve his privacy: he would sell Zuckerberg the entire property if the Facebook billionaire would introduce the developer to his important Silicon Valley contacts. According to Voskerician's suit, the two parties agreed on this, though it was never put in writing.

Voskerician writes in an April 13, 2013 email to Zuckerberg:

"Mr. Zuckerberg, First I am happy that I could maintain your privacy by selling you the Hamilton property. Second, I wanted to meet and shake hands for the transaction and discuss your offering of working with you in the future as you stated you have built Facebook on connections that you have with others in Silicon Valley. One of the reasons I went with your offer other than maintaining your privacy was your offering to help me get my homes, development projects, in front of your Facebook employees and build a relationship with you."

Voskerician expressed interest in discussing a project with Zuckerberg, one that used "modern science based sustainable social living" on an "open source" model.

Emails between Zuckerberg and his inner circle indicate that the Facebook chief had no intention of helping Voskerician other than in a "light" way.

In an email, Divesh Makan, a financial adviser to Zuckerberg, says Voskerician's offer to maintain the CEO's privacy on these conditions was an "obscene proposal."

In another, Zuckerberg's wife, Priscilla Chan, writes, "It's stuff like this that makes me so sad and angry."

Zuckerberg's lawyers are calling Voskerician's offers "extortive."

Zuckerberg paid Voskerician $1.7 million for the rights to the property, then bought the lot from its owners for $4.8 million, according to county records. But Voskerician claims his interest in the property was worth far more than $1.7 million, and that he gave Zuckerberg a discount because of the business his referrals would potentially bring in.

Makan's firm later bought the three other homes around Zuckerberg's house, further guaranteeing his privacy. The homes were purchased for $10.5 million, $14 million, and $14.5 million, according to county records.