Exhibit 10.13

4 Maguire Road

Lexington, MA

PURCHASE AND SALE AGREEMENT

by and between

4 MAGUIRE ROAD REALTY TRUST

as Seller,

and

SENIOR HOUSING PROPERTIES TRUST,

as Purchaser

May 5, 2008

TABLE OF CONTENTS

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PURCHASE AND SALE AGREEMENT

THIS PURCHASE AND SALE AGREEMENT is made as of May 5, 2008, by and between 4 MAGUIRE ROAD REALTY TRUST , a Massachusetts nominee trust (the “ Seller ”), and SENIOR HOUSING PROPERTIES TRUST , a Maryland real estate investment trust (the “ Purchaser ”).

WITNESSETH :

WHEREAS, the Seller is the owner of the Property (this and other capitalized terms used and not otherwise defined herein shall have the meanings given such terms in Section 1 ); and

WHEREAS, the Seller wishes to sell to the Purchaser, and the Purchaser desires to purchase from the Seller, the Property, subject to and upon the terms and conditions hereinafter set forth;

NOW, THEREFORE , in consideration of the mutual covenants herein contained and other good and valuable consideration, the mutual receipt and legal sufficiency of which are hereby acknowledged, the Seller and the Purchaser hereby agree as follows:

SECTION 1.                           DEFINITIONS .

Capitalized terms used in this Agreement shall have the meanings set forth below or in the section of this Agreement referred to below:

1.1.                                                  “ Agreement ”  shall mean this Purchase and Sale Agreement, together with any exhibits and schedules attached hereto, as it and they may be amended from time to time as herein provided.

1.2.                                                  “ Business Day ”  shall mean any day other than a Saturday, Sunday or any other day on which banking institutions in The Commonwealth of Massachusetts are authorized by law or executive action to close.

1.3.                                                  “ Closing ”  shall have the meaning given such term in Section 2.2 .

1.4.                                                  “ Closing Date ”  shall have the meaning given such term in Section 2.2 .

1.5.                                                  “ Existing Survey ”   shall mean the existing ALTA survey of the Property.

1.6.                                                  “ Existing Title Policy ”   shall mean, the existing title insurance policy for the Property.

1.7.                                                  “ Improvements ”   shall mean, the Seller’s entire right, title and interest in and to the existing office buildings, fixtures and other structures and improvements situated on, or affixed to, the Land.

1.8.                                                  “ Land ”  shall mean, the Seller’s entire right, title and interest in and to (a) the parcel(s) of land described in Schedule A hereto, together with (b) all easements, rights of way, privileges, licenses and appurtenances which the Seller may own with respect thereto.

1.9.                                                  “ Leases ”  shall mean the leases identified in the Rent Roll and any other leases hereafter entered into in accordance with the terms of this Agreement.

1.10.                                            “ Other Property ”   shall mean the Seller’s entire right, title and interest in and to (a) all fixtures, machinery, systems, equipment and items of personal property owned by the Seller and attached or appurtenant to, located on and used in connection with the ownership, use, operation or maintenance of the Land or Improvements, if any, and (b) all intangible property owned by the Seller arising from or used in connection with the ownership, use, operation or maintenance of the Land or Improvements, if any.

1.11.                                            “ Permitted Exceptions ”  shall mean, collectively, (a) liens for taxes, assessments and governmental charges not yet due and payable or due and payable but not yet delinquent; (b) the Leases; (c) the exceptions to title set forth in the Existing Title Policy; (d) all matters shown on the Existing Survey, and (e) such other nonmonetary encumbrances with respect to the Property as may be shown on the Update which are not objected to by the Purchaser (or which are objected to, and subsequently waived, by the Purchaser) in accordance with Section 3.1 .

1.12.                                            “ Property ”  shall mean, collectively, all of the Land, the Improvements and the Other Property.

1.13.                                            “ Purchase Price ”  shall mean Nineteen Million Four Hundred Seventy-Four Thousand Three Hundred Eighty-Eight Dollars ($19,474,388).

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1.14.                                            “ Purchaser ”  shall have the meaning given such term in the preambles to this Agreement, together with any permitted successors and assigns.

1.15.                                            “ Rent Roll ”  shall mean Schedule B to this Agreement.

1.16.                                            “ Seller ”  shall have the meaning given such term in the preambles to this Agreement, together with any permitted successors and assigns.

1.17.                                            “ Title Company ”  shall mean Lawyers Title Insurance Corporation.

1.18.                                            “ Update ”   shall have the meaning given such term in Section 3.1 .

SECTION 2.                           PURCHASE AND SALE; CLOSING .

2.1.                                                  Purchase and Sale .   In consideration of the payment of the Purchase Price by the Purchaser to the Seller and for other good and valuable consideration, the Seller hereby agrees to sell to the Purchaser, and the Purchaser hereby agrees to purchase from the Seller, the Property for the Purchase Price, subject to and in accordance with the terms and conditions of this Agreement.

2.2.                                                  Closing .   The purchase and sale of the Property shall be consummated at a closing (the “ Closing ”) to be held at the offices of Sullivan & Worcester LLP, One Post Office Square, Boston, Massachusetts, or at such other location as the Seller and the Purchaser may agree, at 10:00 a.m., local time, on January 30, 2009, as the same may be accelerated pursuant to this Section 2.2 (the “ Closing Date ” ).

Notwithstanding the foregoing, either party may accelerate the Closing Date by giving not less than ten (10) Business Days prior written notice (an “ Acceleration Notice ”) to the other, in which event the Closing Date shall be the date set forth in such Acceleration Notice unless the party receiving the Acceleration Notice gives written notice objecting to the accelerated date set forth in the Acceleration Notice (a “ Rejection Notice ”) to the other within five (5) Business Days after its receipt of the Acceleration Notice, in which event, the Closing Date shall not be accelerated but shall occur as set forth in the preceding paragraph; provided , however , that the Seller shall have the right to give a Rejection Notice only if the acceleration of the Closing Date will adversely effect the Seller’s ability to

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conclude a like kind exchange pursuant to Section 12.15 , and the Purchaser shall have the right to give a Rejection Notice only if the Purchaser is unable to satisfy the condition in Section 4.2 prior to such accelerated Closing Date.

2.3.                                                  Purchase Price .

(a)                                 At Closing, the Purchaser shall pay the Purchase Price to the Seller, subject to the following adjustments:

(i)                                                There shall be added to, or deducted from, the Purchase Price such amounts as may be required by Article 9 .

(b)                                The Purchase Price, as adjusted as provided herein, shall be payable by wire transfer of immediately available funds on the Closing Date to an account or accounts to be designated by the Seller.

SECTION 3.                                               TITLE, DILIGENCE MATERIALS, ETC .

3.1.                                                  Title .  Prior to the execution of this Agreement, the Seller has delivered the Existing Title Policy and the Existing Survey to the Purchaser.

Within ten (10) days after the execution hereof, the Purchaser shall order an update to the Existing Title Policy (an “ Update ”) from the Title Company.  The Purchaser shall deliver to the Seller a copy of the Update promptly upon receipt thereof.  Promptly after receipt of the Update, but, in any event, prior to the Closing Date, the Purchaser shall give the Seller written notice of any title exceptions (other than Permitted Exceptions) set forth on the Update as to which the Purchaser objects.  The Seller shall have the right, but not the obligation, to attempt to remove, satisfy or otherwise cure any exceptions to title to which the Purchaser so objects.  If, for any reason, in its sole discretion, the Seller is unable or unwilling to take such actions as may be required to cause such exceptions to be removed from the Update, the Seller shall give the Purchaser notice thereof; it being understood and agreed that the failure of the Seller to give prompt notice of objection shall be deemed an election by the Seller not to remedy such matters.  If the Seller shall be unable or unwilling to remove any title defects to which the Purchaser has so objected, the Purchaser may elect (i) to terminate this Agreement or (ii) to consummate the transactions contemplated hereby, notwithstanding such title defect, without any abatement or reduction in the Purchase Price on account thereof (whereupon

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such objected to exceptions or matters shall be deemed to be Permitted Exceptions).  The Purchaser shall make any such election by written notice to the  Seller given on or prior to the fifth (5 ^th ) Business Day after the Seller’s notice of its unwillingness or inability to cure (or deemed election not to cure) such defect and time shall be of the essence with respect to the giving of such notice.  Failure of the Purchaser to give such notice shall be deemed an election by the Purchaser to proceed in accordance with clause (ii) above.

3.2.                                                  No Other Diligence .  The Purchaser acknowledges that, except as provided in Section 3.1 , (i) the Purchaser has had the opportunity to fully investigate and inspect the physical and environmental condition of the Property, and to review and analyze all title examinations, surveys, environmental assessment reports, building evaluations, financial data and other investigations and materials pertaining to the Property which the Purchaser deems necessary to determine the feasibility of the Property and its decision to acquire the Property, (ii) the Purchaser shall not be conducting any further title examinations, surveys, environmental assessments, building evaluations, financial analyses or other investigations with respect to the Property, and (iii) the Purchaser shall not have any right to terminate this Agreement as a result of any title examinations, surveys, environmental assessments, building valuations, financial analyses or other investigations with respect to the Property.

SECTION 4.                           CONDITIONS TO THE PURCHASER’S OBLIGATION TO CLOSE .

The obligation of the Purchaser to acquire the Property shall be subject to the satisfaction of the following conditions precedent on and as of the Closing Date:

4.1.                                                  Closing Documents .  The Seller shall have delivered, or cause to have been delivered, to the Purchaser the following:

(a)                                   A good and sufficient deed in the form attached as Schedule C hereto, with respect to the Property, in proper statutory form for recording, duly executed and acknowledged by the Seller, conveying title to the Property, free from all liens and encumbrances other than the Permitted Exceptions;

(b)                                  An assignment by the Seller and an assumption by the Purchaser, in form and substance reasonably satisfactory to the Seller and the Purchaser, duly executed and acknowledged by the Seller and the Purchaser, of all of the Seller’s right, title

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and interest in, to and under the Leases and all of the Seller’s right, title and interest, if any, in, to and under all transferable licenses, contracts, permits and agreements affecting the Property;

(c)                                   A bill of sale by the Seller, without warranty of any kind, in form and substance reasonably satisfactory to the Seller and the Purchaser, with respect to any personal property owned by the Seller, situated at the Property and used exclusively by the Seller in connection with the Property (it being understood and agreed that no portion of the Purchase Price is allocated to personal property);

(d)                                  To the extent the same are in the Seller’s possession, original, fully executed copies of all material documents and agreements, plans and specifications and contracts, licenses and permits pertaining to the Property;

(e)                                   To the extent the same are in the Seller’s possession, duly executed original copies of the Leases;

(f)                                     A closing statement showing the Purchase Price, apportionments and fees, and costs and expenses paid in connection with the Closing; and

(g)                                  Such other conveyance documents, certificates, deeds and other instruments as the Purchaser, the Seller or the Title Company may reasonably require and as are customary in like transactions in sales of property in similar transactions.

4.2.                                                  Financing .  The Purchaser shall have, in addition to funds available to the Purchaser on date of this Agreement, secured sufficient additional funds, whether by means of capital market transactions, bank financings or otherwise, to consummate the transactions contemplated hereby.

4.3.                                                  Title Policy .  The Title Company shall be prepared to issue, upon payment of the title premium at its regular rates, a title policy in the amount of the Purchase Price, insuring title to the Property is vested in the Purchaser or its designee or assignee, subject only to the Permitted Exceptions, with such endorsements as shall be reasonably required by the Purchaser.

4.4.                                                  Environmental Reliance Letters .  The Purchaser shall have received a reliance letter, authorizing the Purchaser and its designees and assignees to rely on the most recent

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environmental assessment report prepared for the Property, in form and substance reasonably acceptable to t he Purchaser.

4.5.                                                  Condition of Property .  The Property shall be in substantially the same physical condition as on the date of this Agreement, ordinary wear and tear and, subject to Section 10.1 , casualty excepted.

4.6.                                                  Other Conditions .  All representations and warranties of the Seller herein shall be true, correct and complete in all material respects on and as of the Closing Date and the Seller shall have performed in all material respects all covenants and obligations required to be performed by the Seller on or before the Closing Date.

SECTION 5.                           CONDITIONS TO SELLER’S OBLIGATION TO CLOSE .

The obligation of the Seller to convey the Property to the Purchaser is subject to the satisfaction of the following conditions precedent on and as of the Closing Date:

5.1.                                                  Purchase Price .   The Purchaser shall deliver to the Seller the Purchase Price payable hereunder, subject to the adjustments set forth in Section 2.3 , together with any closing costs to be paid by the Purchaser under Section 9.2 .

5.2.                                                  Closing Documents .  The Purchaser shall have delivered to the Seller duly executed and acknowledged counterparts of the documents described in Section 4.1 , where applicable.

5.3.                                                  Other Conditions .  All representations and warranties of the Purchaser herein shall be true, correct and complete in all material respects on and as of the Closing Date and the Purchaser shall have performed in all material respects all covenants and obligations required to be performed by the Purchaser on or before the Closing Date.

SECTION 6.                           REPRESENTATIONS AND WARRANTIES OF SELLER .

To induce the Purchaser to enter into this Agreement, the Seller represents and warrants to the Purchaser as follows:

6.1.                                                  Status and Authority of the Seller, Etc.   The Seller is duly organized, validly existing and in good standing under the laws of its state of organization or formation, and has all requisite power and authority under its charter documents to

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enter into and perform its obligations under this Agreement and to consummate the transactions contemplated hereby.

6.2.                                                  Action of the Seller, Etc.   The Seller has taken all necessary action to authorize the execution, delivery and performance of this Agreement, and upon the execution and delivery of any document to be delivered by the Seller on or prior to the Closing Date, this Agreement and such document shall constitute the valid and binding obligation and agreement of the Seller, enforceable against the Seller in accordance with its terms, except as enforceability may be limited by bankruptcy, insolvency, reorganization, moratorium or similar laws of general application affecting the rights and remedies of creditors.

6.3.                                                  No Violations of Agreements .  Neither the execution, delivery or performance of this Agreement by the Seller, nor compliance with the terms and provisions hereof, will result in any breach of the terms, conditions or provisions of, or conflict with or constitute a default under, or result in the creation of any lien, charge or encumbrance upon the Property pursuant to the terms of any indenture, mortgage, deed of trust, note, evidence of indebtedness or any other agreement or instrument by which the Seller is bound.

6.4.                                                  Litigation .  To the Seller’s actual knowledge, it has not received written notice that any investigation, action or proceeding is pending or threatened, which (i) questions the validity of this Agreement or any action taken or to be taken pursuant hereto, or (ii) involves condemnation or eminent domain proceedings against the Property or any portion thereof.

6.5.                                                  Existing Leases, Etc.   Subject to Section 8.1 , other than the Leases listed in the Rent Roll, the Seller has not entered into a contract or agreement with respect to the occupancy of the Property that will be binding on the Purchaser after the Closing.  To the Seller’s actual knowledge: (a) the copies of the Leases heretofore delivered by the Seller to the Purchaser are true, correct and complete copies thereof; and (b) such Leases have not been amended except as evidenced by amendments similarly delivered and constitute the entire agreement between the Seller and the tenants thereunder.  Except as otherwise set forth in the Rent Roll or the Leases: (i) to the Seller’ actual knowledge, each of its Leases is in full force and effect on the terms set forth therein; (ii) to the Seller’s actual knowledge, there are no uncured defaults or circumstances which with the giving of notice, the passage of time or both would constitute a default thereunder which would

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have a material adverse effect on the business or operations of the Property; (iii) to the Seller’s actual knowledge, each of its tenants is legally required to pay all sums and perform all material obligations set forth therein without any ongoing concessions, abatements, offsets, defenses or other basis for relief or adjustment; (iv) to the Seller’s actual knowledge, none of its tenants has asserted in writing or has any defense to, offsets or claims against, rent payable by it or the performance of its other obligations under its Lease which would have a material adverse effect on the on-going business or operations of the Property; (v) the Seller has no outstanding obligation to provide any of its tenants with an allowance to perform, or to perform at its own expense, any tenant improvements; (vi) none of its tenants has prepaid any rent or other charges relating to the post-Closing period; (vii) to the Seller’s actual knowledge, none of its tenants has filed a petition in bankruptcy or for the approval of a plan of reorganization or management under the Federal Bankruptcy Code or under any other similar state law, or made an admission in writing as to the relief therein provided, or otherwise become the subject of any proceeding under any federal or state bankruptcy or insolvency law, or has admitted in writing its inability to pay its debts as they become due or made an assignment for the benefit of creditors, or has petitioned for the appointment of or has had appointed a receiver, trustee or custodian for any of its property, in any case that would have a material adverse effect on the business or operations of the Property; (viii) to the Seller’s actual knowledge, none of its tenants has requested in writing a modification of its Lease, or a release of its obligations under its Lease in any material respect or has given written notice terminating its Lease, or has been released of its obligations thereunder in any material respect prior to the normal expiration of the term thereof, in any case that would have a material adverse effect on the on-going business or operations of the Property; (ix) to the Seller’s actual knowledge, except as set forth in the Leases, no guarantor has been released or discharged, voluntarily or involuntarily, or by operation of law, from any obligation under or in connection with any of its Leases or any transaction related thereto; and (x) all brokerage commissions currently due and payable with respect to each of its Leases have been paid.  To the Seller’s actual knowledge, the other information set forth in the Rent Roll is true, correct and complete in all material respects.

6.6.                                                  Agreements, Etc.   Other than the Leases, the Seller has not entered into any contract or agreement with respect to

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the Property which will be binding on the Purchaser after the Closing other than contracts and agreements being assumed by the Purchaser or which are terminable upon thirty (30) days notice without payment of premium or penalty.

6.7.                                                  Not a Foreign Person .   The Seller is not a “foreign person” within the meaning of Section 1445 of the United States Revenue Code of 1986, as amended, and the regulations promulgated thereunder.

The representations and warran