Shares of

Plumtree Software

(PLUM)

soared Wednesday after the softwaremaker received an unsolicited bid to be acquired by a San Francisco-basedfirm just three months after its IPO.

Shares of San Francisco-based Plumtree jumped 58 cents, or 20.9%, to$3.35 in recent trading.

In a letter Tuesday to Plumtree CEO John Kunze, San Francisco-basedSutter Opportunity Fund offered to acquire all outstanding shares ofPlumtree for $5 per share. Sutter would pay $2 in cash and $3 in the formof an 8% note maturing in five years. The total purchase price would beabout $147 million.

The offer, which expires Sept. 10, represents a premium of 80.5% over Tuesday's closing price of $2.77.

But the deal may be difficult to swallow because it alsorepresents a 41.2% discount from Plumtree's initial public offeringprice of $8.50. The company, which makes corporate portal software, wentpublic June 3.

"You have two issues -- it's above the current market

price butbelow the June 3 offering price," said Steve Ashley, an analyst withRobert W. Baird & Company. "That is the board's quandary." Ashley, whohas a neutral rating on Plumtree, said he did not yet have an opinion onthe offer price. His company hasn't done any banking with Plumtree.

Sutter's offer is subject to certain terms and conditions, includingapproval of the Plumtree board of directors. In a statement Wednesday,Plumtree said the board will evaluate the terms of the offer "in duecourse." Prior to receiving the offer, Plumtree had no contact withSutter, Plumtree said in the statement.

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A Plumtree spokeswoman declinedto comment when asked if the company has received other offers. Aspokesperson from Sutter was not immediately available for comment.

Plumtree, which went public at a difficult time for the market and ITspending after receiving VC funding from big name investors such as

Intel

(INTC) - Get Intel Corporation (INTC) Report

and Sequoia Capital, was viewed by some on Wall Street as an eventualacquisition target rather than a standalone company in the long term.But the Sutter offer still was unusual because it came so soon after thecompany's IPO and it came from a financial institution rather than afellow software maker.

"You have a pure financial buyer as opposed to a strategic buyer,"who sees an opportunity for synergies, Ashley said. The interest from afinancial buyer indicates that the company is simply viewed asundervalued, he said.

Sutter has been shopping around for some speculative buys and recently offered to purchase shares of trusts holding securities issued by

WorldCom

, as well as outstanding shares of

Stonehaven Realty Trust

(RPP)

. Stonehaven, whose shares are currently trading at 16 cents, rejected Sutter's offer in July.