8. Unsecured Exchangeable Senior Notes

The following summarizes the unsecured exchangeable senior notes outstanding as of December 31, 2011 (dollars in thousands):


	Coupon/ Stated Rate			Effective Rate(1)			Exchange Rate			Principal Amount			First Optional Redemption Date by Company	Maturity Date
3.625% Exchangeable Senior Notes		3.625	%		4.037	%		8.5051	(2)	$	747,500		N/A	February 15, 2014
2.875% Exchangeable Senior Notes		2.875	%		3.462	%		7.0430	(3)		576,194		February 20, 2012(4)	February 15, 2037
3.750% Exchangeable Senior Notes		3.750	%		3.787	%		10.0066	(5)		450,000		May 18, 2013(6)	May 15, 2036

Total principal											1,773,694
Net unamortized discount											(3,462	)
Adjustment for the equity component allocation, net of accumulated amortization											(54,547	)

Total										$	1,715,685

(1)	Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.

(2)

The initial exchange rate is 8.5051 shares per $1,000 principal amount of the notes (or an initial exchange price of approximately $117.58 per share of Boston Properties, Inc.'s common stock). In addition, the Company entered into capped call transactions with affiliates of certain of the initial purchasers, which are intended to reduce the potential dilution upon future exchange of the notes. The capped call transactions were intended to increase the effective exchange price to the Company of the notes from $117.58 to approximately $137.17 per share (subject to adjustment), representing an overall effective premium of approximately 40% over the closing price on August 13, 2008 of $97.98 per share of Boston Properties, Inc.'s common stock. The net cost of the capped call transactions was approximately $44.4 million. As of December 31, 2011, the effective exchange price was $135.25 per share.

(3)

In connection with the special distribution of $5.98 per share of Boston Properties, Inc.'s common stock declared on December 17, 2007, the exchange rate was adjusted from 6.6090 to 7.0430 shares per $1,000 principal amount of notes effective as of December 31, 2007, resulting in an exchange price of approximately $141.98 per share of Boston Properties, Inc.'s common stock (See Note 20).

(4)

Holders may require the Operating Partnership to repurchase the notes for cash on February 15, 2012, 2017, 2022, 2027 and 2032 and at any time prior to their maturity upon a fundamental change, in each case at a price equal to 100% of the principal amount of the notes being repurchased plus any accrued and unpaid interest up to, but excluding, the repurchase date. The Operating Partnership repurchased/redeemed the notes for cash in February 2012 at a price equal to 100% of the principal amount of the notes being repurchased/redeemed plus any accrued and unpaid interest up to, but excluding, the repurchase/redemption date (See Note 20).

(5)

In connection with the special distribution of $5.98 per share of Boston Properties, Inc.'s common stock declared on December 17, 2007, the exchange rate was adjusted from 9.3900 to 10.0066 shares per $1,000 principal amount of notes effective as of December 31, 2007, resulting in an exchange price of approximately $99.93 per share of Boston Properties, Inc.'s common stock.

(6)

Holders may require the Operating Partnership to repurchase the notes for cash on May 18, 2013 and May 15, 2016, 2021, 2026 and 2031 and at any time prior to their maturity upon a fundamental change, in each case at a price equal to 100% of the principal amount of the notes being repurchased plus any accrued and unpaid interest up to, but excluding, the repurchase date.

ASC 470-20 (formerly known as FSP No. APB 14-1) requires the liability and equity components of convertible debt instruments that may be settled in cash upon conversion (including partial cash settlement) to be separately accounted for in a manner that reflects the issuer's nonconvertible debt borrowing rate. ASC 470-20 requires that the initial proceeds from the sale of the Operating Partnership's $862.5 million of 2.875% exchangeable senior notes due 2037, $450.0 million of 3.75% exchangeable senior notes due 2036 and $747.5 million of 3.625% exchangeable senior notes due 2014 be allocated between a liability component and an equity component in a manner that reflects interest expense at the interest rate of similar nonconvertible debt that could have been issued by the Operating Partnership at such time. The Company measured the fair value of the debt components of the 2.875%, 3.75% and 3.625% exchangeable senior notes for the periods presented based on effective interest rates of 5.630%, 5.958% and 6.555%, respectively. The aggregate carrying amount of the debt component was approximately $1.72 billion and $1.72 billion (net of the ASC 470-20 adjustment of approximately $54.5 million and $93.6 million) at December 31, 2011 and December 31, 2010, respectively. As a result, the Company attributed an aggregate of approximately $230.3 million of the proceeds to the equity component of the notes, which represents the excess proceeds received over the fair value of the notes at the date of issuance. The equity component of the notes has been reflected within Additional Paid-in Capital in the Consolidated Balance Sheets. The Company reclassified approximately $1.0 million of deferred financing costs to Additional Paid-in Capital, which represented the costs attributable to the equity components of the notes. The carrying amount of the equity component was approximately $202.5 million and $207.1 million at December 31, 2011 and December 31, 2010, respectively. The resulting debt discount will be amortized over the period during which the debt is expected to be outstanding (i.e., through the first optional redemption dates or, in the case of the 2014 notes, the maturity date) as additional non-cash interest expense. The additional non-cash interest expense attributable to each debt security will increase in subsequent reporting periods through the first optional redemption date (or, in the case of the 2014 notes, the maturity date) as the debt accretes to its par value over the same period. The aggregate contractual interest expense was approximately $66.3 million, $69.0 million and $74.4 million for the years ended December 31, 2011, 2010 and 2009, respectively. As a result of applying ASC 470-20, the Company reported additional non-cash interest expense of approximately $38.8 million, $38.3 million and $38.6 million for the years ended December 31, 2011, 2010 and 2009, respectively. ASC 470-20 requires companies to retrospectively apply the requirements of the pronouncement to all periods presented.

On November 9, 2011, the Company's Operating Partnership repurchased $50.0 million aggregate principal amount of its 2.875% exchangeable senior notes due 2037 for approximately $50.2 million. The repurchased notes had an aggregate carrying value of approximately $49.6 million at the time of repurchase resulting in the recognition of a loss on early extinguishment of debt of approximately $0.6 million during the year ended December 31, 2011. There remains an aggregate of approximately $576.2 million of these notes outstanding (See Note 20).