The boards of Genzyme Corp and Sanofi-Aventis SA are scheduled to meet on Sunday to discuss Sanofi's proposed acquisition of Genzyme, according to sources with knowledge of the situation.

The deal is expected to be priced at $74 in cash, or $19.2 billion, based on Genzyme's outstanding shares of 258.99 million as of October 29, plus a contingent value right, or CVR, with an intrinsic value of $5 to $6 a share, the sources said.

Sanofi, a French-based drugmaker, took its initial bid of $69 a share directly to Genzyme shareholders in October, but the two companies in recent weeks have entered direct negotiations on a higher price.

The CVR is a tradable instrument, which promises a payout to shareholders over time based on the performance of Genzyme's experimental drug Lemtrada for multiple sclerosis.

It is not possible to pin down what the CVR will begin to trade at, but assuming it trades for $2 a share -- a reasonable estimate since many of Genzyme's shareholders are short-term investors who will want to sell immediately -- the deal would give Genzyme a tradable value of about $19.68 billion.

An agreement has not yet been finalized as Sanofi is still reviewing Genzyme's business and an agreement may not be announced until next week.

The nominal value of the CVR is expected to be between $12 and $15, to be paid out over a time period of seven or eight years, according to one source.

But a standard discount is applied to those figures to determine their present value. That figure is then risk-adjusted depending on investors' assessment of the likelihood of the company meeting its goals.

(Reporting by Toni Clarke and Jessica Hall; Editing by Peter Cooney)