The formal statement from the US drugs giant over the Bank Holiday weekend sent shares in the UK-based pharmaceuticals maker down 76p, to 4252p, leaving its market value below £54 billion - more than £15 billion under its American suitor's offer.
The wider FTSE 100 Index was in a better mood after the Bank Holiday, up 29.2 points to 6844.9, as it caught up following gains on European markets on Monday.
Investors were buoyed by the hopes that Russia's acceptance of the election of a new Ukrainian president would lead to an easing of tensions. Stocks on the continent were also boosted by comments from European Central Bank president Mario Draghi suggesting further stimulus measures may be needed to fend off the threat of deflation.
Germany's Dax was up while France's Cac 40 was flat. In New York, the Dow Jones Industrial Average was also up at the time of the close in London. On currency markets, sterling was down against the dollar, at 1.68, and against the euro, at 1.23, in the wake of uncertainty following European election results and weak mortgage approval figures.
In London, Astra's price had been boosted in recent weeks by the increasing pressure from Pfizer to make a deal, with a final offer valuing it at £55 per share.
But it repeatedly rebuffed the Viagra maker's advances.Analysts at Panmure Gordon slashed their target price for the UK firm, saying a likely change in US tax rules might hit any plans Pfizer could hatch to come back for a second attempt.
Elsewhere in the top-flight, Intercontinental Hotels Group rose strongly on reports that it had rebuffed a £6 billion bid. Shares rose three per cent, or 76p to 2302p.Meanwhile, Lloyds Banking Group rose nearly 2 per cent or 1.2p, to 77.2p after it announced it was to float a quarter of its TSB business next month.
On the FTSE 250, shares in engineering data and IT systems provider Aveva closed up 8.7%, or 189pp, to 2350p, after a well received set of annual results.
Adjusted pre-tax profits were up 11% to £78.3 million while the final dividend was hiked by 13% and profit margin also grew.
Chief executive Richard Longdon said it was confident it could achieve targets for further growth. Analysts at Panmure Gordon said results - for the year to the end of March - were better than expected.
The biggest FTSE 100 risers were Arm Holdings up 35p to 917p, International Consolidated Airlines Group up 13.5p to 392.9p, Intercontinental Hotels up 76p at 2302p and Travis Perkins up 54p at 1724p.
The biggest fallers were Fresnillo down 27p at 822p, AstraZeneca down 76p at 4252p, Randgold Resources down 77p at 4428p and Sainsbury's down 4.7p at 399p.