GREENSTREET
      ACQUISITION CORP.

    


    SPONSOR
      WARRANTS SUBSCRIPTION AGREEMENT

    


    THIS
      SPONSOR WARRANTS SUBSCRIPTION AGREEMENT
      (this
“Agreement”) is made as of the 14th day of January, 2008, by and between
      Greenstreet Acquisition Corp., a Delaware corporation (the “Company”), and Duke
      K. Bristow Ph. D. (“Purchaser”).

    


    WHEREAS,
      the
      Company desires to commit to issue and sell, and Purchaser desires to commit
      to
      purchase and acquire, Warrants (as defined herein) on the terms and conditions
      hereinafter set forth;

    


    NOW,
      THEREFORE, for and in consideration of the promises and mutual covenants set
      forth herein, it is agreed between the parties as follows:

    


    1.
      Commitment
      To Purchase Warrants.
      Subject
      to and immediately prior to the consummation of the Company’s initial public
      offering (the “IPO”), Purchaser hereby agrees to subscribe for and purchase from
      the Company, and the Company hereby agrees to issue and sell to
      Purchaser, 15,000 warrants (each a “Warrant”) at a purchase price of $1.00
      per Warrant for an aggregate purchase price of $15,000. Each Warrant shall
      entitle the holder thereof to purchase one share of the common stock of the
      Company, par value $0.001 per share (the “Common Stock”) at an exercise price of
      $6.00, in accordance with the terms of the Warrant as set forth in the Warrant
      Agreement (the “Warrant Agreement”) dated as of December 14, 2007 by and between
      the Company and American Stock Transfer & Trust Company, as warrant agent.
      The closing of the purchase and sale of the Warrants hereunder, including
      payment for and delivery of the Warrants, shall occur at the offices of the
      Company immediately prior to, and subject to consummation of, the
      IPO.

    


    2.
      Payment
      of Purchase Price.
      The
      purchase price for the Warrants (also referred to herein as the “Securities”)
      shall be tendered in full at the closing by one or a combination of the
      following means:

    


    (a)
      wiring of immediately available United States funds to an account for the
      benefit of the Company, pursuant to wire instructions provided by the Company
      in
      advance; or

    


    (b)
      by
      delivery of a cashiers check to the Company of immediately available United
      States funds.

    


    3.
      Acceptance
      or Rejection of Agreement.
      The
      Company has the right to reject this Agreement and any subscription for the
      Securities represented hereby in whole or in part, for any reason and at any
      time prior to a closing, notwithstanding receipt by Purchaser or prior notice
      of
      acceptance of such subscription. The Securities subscribed for herein will
      not
      be deemed issued to or owned by Purchaser until a copy of this Agreement has
      been executed by the Company and Purchaser and a closing with respect to such
      Securities has occurred. In the event that a closing does not take place for
      any
      reason with respect to some or all of the Securities, all cash proceeds
      delivered by Purchaser in accordance herewith with respect to such Securities
      shall be returned to Purchaser as soon as practicable, without interest, offset
      or deduction.

     

    
      
        
        

      

      
        1

        
          

        

      

      
        
        

      

    

     

    4.
      Limitations
      on Transfer.
      Purchaser shall not assign, hypothecate, donate, encumber or otherwise dispose
      of any interest in the Warrants (and any shares of Common Stock issuable in
      respect thereof) during the “Escrow Period” for the “Sponsor Warrants” (as such
      terms are defined in a securities escrow agreement substantially in the form
      attached hereto as Exhibit A (the “Securities Escrow Agreement”), dated on or
      about the effective date of the IPO to be entered into by and between the
      Company and an escrow agent to be determined by the Company), except (i) as
      otherwise permitted by the Securities Escrow Agreement, (ii) in compliance
      with
      applicable securities laws and (iii) in compliance with the Warrant
      Agreement.

    


    5.
      Restrictive
      Legends.
      All
      certificates representing the Securities (and any underlying securities thereof)
      shall have endorsed thereon legends in substantially the following forms (in
      addition to any other legend which may be required by other agreements between
      the parties hereto):

    


    (a)
“THE
      SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED. THE SECURITIES MAY NOT BE SOLD, OFFERED
      FOR
      SALE, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION
      STATEMENT AS TO THE SECURITIES UNDER SAID ACT OR AN OPINION OF COUNSEL
      SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT
      REQUIRED.”

    


    (b)
“THE
      SECURITIES REPRESENTED BY THIS CERTIFICATE MAY NOT BE ASSIGNED, HYPOTHECATED,
      DONATED, ENCUMBERED, SOLD, TRANSFERRED OR OTHERWISE DISPOSED OF EXCEPT IN
      ACCORDANCE WITH THAT CERTAIN SECURITIES ESCROW AGREEMENT DATED ____________,
      2008, AND THAT CERTAIN WARRANT AGREEMENT DATED AS OF DECEMBER 14, 2007, COPIES
      OF WHICH ARE AVAILABLE FOR INSPECTION AT THE OFFICES OF THE
      COMPANY.”

    


    (c)
      Any
      legend required by appropriate blue sky officials.

    


    6.
      Investment
      Representations.
      In
      connection with the purchase of the Securities, Purchaser represents to the
      Company the following:

    


    (a)
      Purchaser has been furnished with all materials relating to the Company’s
      business affairs and financial condition and materials related to the offer
      and
      sale of the Securities that have been requested by Purchaser and has acquired
      sufficient information about the Company to reach an informed and knowledgeable
      decision to acquire the Securities. Purchaser has been afforded the opportunity
      to ask questions of the executive officer and director of the Company. Purchaser
      understands that its investment in the Securities involves a high degree of
      risk. Purchaser has sought such accounting, legal and tax advice as Purchaser
      has considered necessary to make an informed investment decision with respect
      to
      Purchaser’s acquisition of the Securities. Purchaser has such knowledge and
      expertise in financial and business matters, knows of the high degree of risk
      associated with investments generally and particularly investments in the
      securities of companies in the development stage such as the Company, is capable
      of evaluating the merits and risks of an investment in the Securities, and
      is
      able to bear the economic risk of an investment in the Securities in the amount
      contemplated hereunder. Purchaser has adequate means of providing for its
      current financial needs and contingencies and will have no current or
      anticipated future needs for liquidity which would be jeopardized by the
      investment in the Securities. Purchaser can afford a complete loss of its
      investment in the Securities. Purchaser is purchasing the Securities for
      investment for Purchaser’s own account only and not with a view to, or for
      resale in connection with, any “distribution” thereof within the meaning of the
      Securities Act of 1933, as amended (the “Act”). Purchaser understands that the
      Company is a blank check development stage company recently formed for the
      purpose of consummating an initial business combination (a “Business
      Combination”) and understands that there is no assurance as to the future
      performance of the Company and that the Company may never effectuate a Business
      Combination.

     

    
      
        
        

      

      
        2

        
          

        

      

      
        
        

      

    

     

    (b)
      Purchaser understands that the Securities (and the underlying securities
      thereof) have not been registered under the Act or any state securities law
      by
      reason of a specific exemption therefrom, and that the Company is relying on
      the
      truth and accuracy of, and Purchaser’s compliance with, the representations and
      warranties and agreements of Purchaser set forth herein to determine the
      availability of such exemptions and the eligibility of Purchaser to acquire
      such
      Securities, including, but not limited to, the bona fide nature of Purchaser’s
      investment intent as expressed herein.

    


    (c)
      Purchaser further acknowledges and understands that the Securities (and the
      underlying securities thereof) must be held indefinitely unless the Securities
      (and the underlying securities thereof) are subsequently registered under the
      Act or an exemption from such registration is available. Purchaser understands
      that the certificates evidencing the Securities (and the underlying securities
      thereof) will be imprinted with a legend which prohibits the transfer of the
      Securities (and the underlying securities thereof) unless the Securities (and
      the underlying securities thereof) are registered or such registration is not
      required in the opinion of counsel for the Company.

    


    (d)
      Purchaser is familiar with the provisions of Rule 144 under the Act, as in
      effect from time to time (“Rule 144”), which, in substance, permit limited
      public resale of “restricted securities”
      acquired, directly or indirectly, from the issuer thereof (or from an affiliate
      of such issuer), in a non-public offering subject to the satisfaction of certain
      conditions. Unless the Company registers the Securities (and the underlying
      securities thereof) under the Act, the Securities (and the underlying securities
      thereof) may be resold by Purchaser only in certain limited circumstances
      subject to the provisions of Rule 144, which requires, among other things:
      (i)
      the availability of certain public information about the Company and (ii) the
      resale occurring following the required holding period under Rule 144 after
      Purchaser has purchased, and made full payment of (within the meaning of Rule
      144), the securities to be sold.

    


    (e)
      Purchaser further understands that at the time Purchaser wishes to sell the
      Securities there may be no public market upon which to make such a sale, and
      that, even if such a public market then exists, the Company may not be
      satisfying the current public information requirements of Rule 144, and that,
      in
      such event, Purchaser would be precluded from selling the Securities (and the
      underlying securities thereof) under Rule 144 even if the minimum holding period
      requirement had been satisfied. Notwithstanding Sections 6(d) and (e) hereof,
      Purchaser understands that he may be considered a promoter of the Company and
      understands that it is the position of the Securities and Exchange Commission
      (the “SEC”) that promoters or affiliates of a blank check company and their
      transferees, both before and after a Business Combination, would act as an
      “underwriter” under the Act when reselling the securities of a blank check
      company. Accordingly, the SEC believes that those securities can be resold
      only
      through a registered offering and that Rule 144 would not be available for
      those
      resale transactions despite technical compliance with the requirements of Rule
      144. 

    


    (f)
      Purchaser represents that Purchaser is an “accredited investor” as that term is
      defined in Rule 501 of Regulation D promulgated by the SEC under the Act.


    


    (g)
      Purchaser has all necessary power and authority to enter into this Agreement
      and
      to consummate the transactions contemplated hereby. This Agreement has been
      duly
      executed and delivered by Purchaser. Subject to the terms and conditions of
      this
      Agreement, this Agreement constitutes the valid, binding and enforceable
      obligation of Purchaser, enforceable in accordance with its terms, except as
      enforceability may be limited by (i) applicable bankruptcy, insolvency,
      reorganization, moratorium, fraudulent transfer or similar laws of general
      application now or hereafter in effect affecting the rights and remedies of
      creditors and by general principles of equity (regardless of whether enforcement
      is sought in a proceeding at law or in equity); and (ii) the applicability
      of
      the federal and state securities laws and public policy as to the enforceability
      of the indemnification provisions of this Agreement. The purchase by Purchaser
      of the Securities does not conflict with any material contract by which
      Purchaser or his property is bound, or any laws or regulations or decree, ruling
      or judgment of any court applicable to Purchaser or his property. The principal
      place of business of Purchaser is as set forth on the signature page
      hereto.

     

    
      
        
        

      

      
        3

        
          

        

      

      
        
        

      

    

     

    (h)
      Purchaser did not decide to enter into this Agreement as a result of any general
      solicitation or general advertising within the meaning of Rule 502(c) of the
      Securities Act.

    


    (i)
      Purchaser understands that no United States federal or state agency or any
      other
      government or governmental agency has passed on or made any recommendation
      or
      endorsement of the Securities or the fairness or suitability of the investment
      in the Securities, nor have such authorities passed upon or endorsed the merits
      of the offering of the Securities.

    


    7.
      Company
      Representations and Warranties.
      The
      Company hereby represents and warrants to Purchaser that the Company has all
      necessary corporate power and authority to enter into this Agreement and to
      consummate the transactions contemplated hereby. All corporate action necessary
      to be taken by the Company to authorize the execution, delivery and performance
      of this Agreement and all other agreements and instruments delivered by the
      Company in connection with the transactions contemplated hereby has been duly
      and validly taken and this Agreement has been duly executed and delivered by
      the
      Company. Subject to the terms and conditions of this Agreement, this Agreement
      constitutes the valid, binding and enforceable obligation of the Company,
      enforceable in accordance with its terms, except as enforceability may be
      limited by (i) applicable bankruptcy, insolvency,
      reorganization, moratorium, fraudulent transfer or similar laws of general
      application now or hereafter in effect affecting the rights and remedies of
      creditors and by general principles of equity (regardless of whether enforcement
      is sought in a proceeding at law or in equity); and (ii) the applicability
      of
      the federal and state securities laws and public policy as to the enforceability
      of the indemnification provisions of this Agreement. The sale by the Company
      of
      the Securities does not conflict with the certificate of incorporation or
      by-laws of the Company or any material contract by which the Company or its
      property is bound, or any federal or state laws or regulations or decree, ruling
      or judgment of any United States or state court applicable to the Company or
      its
      property.

    


    8.
      Indemnification.
      Purchaser hereby agrees to indemnify and hold harmless the Company and the
      Company’s officers, directors, stockholders, employees, agents, and attorneys
      against any and all losses, claims, demands, liabilities and expenses (including
      reasonable legal or other expenses incurred by each such person in connection
      with defending or investigating any such claims or liabilities, whether or
      not
      resulting in any liability to such person or whether incurred by the indemnified
      party in any action or proceeding between the indemnitor and indemnified party
      or between the indemnified party and any third party) to which any such
      indemnified party may become subject, insofar as such losses, claims, demands,
      liabilities and expenses (a) arise out of or are based upon any untrue statement
      or alleged untrue statement of a material fact made by Purchaser and contained
      herein, or (b) arise out of or are based upon any breach by Purchaser of any
      representation, warranty or agreement made by Purchaser contained
      herein.

    


    9.
      Miscellaneous.

    


    (a)
      Notices.
      All
      notices required or permitted hereunder shall be in writing and shall be deemed
      effectively given: (i) upon personal delivery to the party to be notified,
      (ii)
      when sent by confirmed facsimile if sent during normal business hours of the
      recipient, and if not during normal business hours of the recipient, then on
      the
      next business day, (iii) five calendar days after having been sent by registered
      or certified mail, return receipt requested, postage prepaid, or (iv) one
      business day after deposit with a nationally recognized overnight courier,
      specifying next day delivery, with written verification of receipt. All
      communications shall be sent to the other party hereto at such party’s address
      hereinafter set forth on the signature page hereof, or at such other address
      as
      such party may designate by ten days advance written notice to the other party
      hereto.

     

    
      
        
        

      

      
        4

        
          

        

      

      
        
        

      

    

     

    (b)
      Successors
      and Assigns.
      This
      Agreement shall inure to the benefit of the successors and assigns of the
      Company and, subject to the restrictions on transfer herein set forth, shall
      be
      binding upon Purchaser and Purchaser’s successors and assigns.

    


    (c)
      Attorneys’
      Fees; Specific Performance.
      Purchaser shall reimburse the Company for all costs incurred by the Company
      in
      enforcing the performance of, or protecting its rights under, any part of this
      Agreement, including reasonable costs of investigation and attorneys’
fees.

    


    (d)
      Governing
      Law; Venue.
      This
      Agreement shall be governed by and construed in accordance with the laws of
      the
      State of Delaware without regard to the principles of conflicts of law thereof.
      The parties agree that any action brought by either party to interpret or
      enforce any provision of this Agreement shall be brought in, and each party
      agrees to, and does hereby, submit to the jurisdiction and venue of, the
      appropriate state or federal court for the district encompassing the Company’s
      principal place of business.

    


    (e)
      Further
      Execution.
      The
      parties agree to take all such further action(s) as may reasonably be necessary
      to carry out and consummate this Agreement as soon as practicable, and to take
      whatever steps may be necessary to obtain any governmental approval in
      connection with or otherwise qualify the issuance of the securities that are
      the
      subject of this Agreement.

    


    (f)
      Independent
      Counsel.
      Purchaser acknowledges that this Agreement has been prepared on behalf of the
      Company by Skadden, Arps, Slate, Meagher & Flom LLP, counsel to the Company
      and that Skadden, Arps, Slate, Meagher & Flom LLP does not represent, and is
      not acting on behalf of, Purchaser. Purchaser has been provided with an
      opportunity to consult with Purchaser’s own counsel with respect to this
      Agreement.

    


    (g)
      Entire
      Agreement; Amendment. This
      Agreement constitutes the entire agreement between the parties with respect
      to
      the subject matter hereof and supersedes and merges all prior agreements or
      understandings, whether written or oral. This Agreement may not be amended,
      modified or revoked, in whole or in part, except by an agreement in writing
      signed by each of the parties hereto.

    


    (h)
      Severability.
      If one
      or more provisions of this Agreement are held to be unenforceable under
      applicable law, the parties agree to renegotiate such provision in good faith.
      In the event that the parties cannot reach a mutually agreeable and enforceable
      replacement for such provision, then (i) such provision shall be excluded from
      this Agreement, (ii) the balance of the Agreement shall be interpreted as if
      such provision were so excluded and (iii) the balance of the Agreement shall
      be
      enforceable in accordance with its terms.

    


    (i)
      Counterparts.
      This
      Agreement may be executed in two or more counterparts, each of which shall
      be
      deemed an original and all of which together shall constitute one instrument.
      This Agreement or any counterpart may be executed via facsimile or electronic
      mail transmission, and any such executed facsimile or electronic mail copy
      shall
      be treated as an original. 

    


    (j)
      Survival.
      The
      representations and warranties contained herein will survive the delivery of,
      and the payment for, the Securities.

    


    (k)
      Waiver
      of Jury Trial.
      Each
      party hereto hereby irrevocably and unconditionally waives the right to a trial
      by jury in any action, suit, counterclaim or other proceeding (whether based
      on
      contract, tort or otherwise) arising out of, connected with or relating to
      this
      Agreement, the transactions contemplated hereby, or the actions of Purchaser
      in
      the negotiation, administration, performance or enforcement hereof.


    


    
      
        
        

      

      
        5

        
          

        

      

      
        
        

      

    



    IN
      WITNESS WHEREOF,
      the
      parties hereto have executed this Agreement as of the day and year first above
      written.

    


    COMPANY:

    


    GREENSTREET
      ACQUISITION CORP. 

    


    


    By:
       /s/
      Jeffrey
      Safchik                             
 

    Name:
       Jeffrey
      Safchik

    Title:
       Chief
      Financial Officer

    


    Address:

    


    


    


    PURCHASER:

    


    


    /s/
      Duke K.
      Bristow                                       
 

    Duke
      K.
      Bristow, Ph. D.

    


    Address:

    


    


    
      
        
        

      

      
        6