Regional bank Synovus slides after $8.6 billion deal with Pinnacle Financial

** Shares of regional lender Synovus Financial SNV slide 10.4% to $50.85 premarket, well below Pinnacle Financial Partners' PNFP buyout offer price of $61.18 apiece

** PNFP slides 8.5% to $95.30 after multiple brokerages downgrade stock on heightened deal execution risk

** Analysts say SNV shares may see some early pressure, given general investor skepticism around merger of equals (MOEs)

** "We have seen several stocks involved in other recent large, high-profile MOEs underperform as investors take a wait and see approach," Raymond James analyst Michael Rose says

** "We continue to like SNV at this valuation and appreciate the 10% premium attained in this transaction, though it is tied to PNFP's stock price and we may see some early pressure, which is typical in a stock merger," RBC analyst Jon Arfstrom says

** PNFP's $8.6 billion all-stock deal for SNV will create a combined bank focused on the fast-growing Southeast markets and with over $100 billion in assets

** As of last close, SNV shares up 10.7% YTD