**Exhibit 31.1**

 

**CERTIFICATIONOF THE CHIEF EXECUTIVE OFFICER PURSUANT TO SECTION 302 OF THE SARBANES-OXLEYACT OF 2002**

 

I, Christoph Westphal, certify that:

 

1. I have reviewed this quarterly report on Form 10-Q of SirtrisPharmaceuticals, Inc.;

 

2. Based on my knowledge, this quarterly report does not contain anyuntrue statement of a material fact or omit to state a material fact necessaryto make the statements made, in light of the circumstances under which suchstatements were made, not misleading with respect to the period covered by thisreport;

 

3. Based on my knowledge, the financial statements, and other financialinformation included in this quarterly report, fairly present in all materialrespects the financial condition, results of operations and cash flows of theregistrant as of, and for, the periods presented in this report;

 

4. The registrant’s other certifying officers and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15(e) and 15d-15(e)) and internal control overfinancial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f))  for the registrant and have:

 

a. Designed suchdisclosure controls and procedures, or caused such disclosure controls and proceduresto be designed under our supervision, to ensure that material informationrelating to the registrant, including its consolidated subsidiaries, is madeknown to us by others within those entities, particularly during the period inwhich this report is being prepared;

 

b. Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

 

c. Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting; and

 

5. The registrant’s other certifying officers and I have disclosed,based on our most recent evaluation of internal control over financialreporting, to the registrant’s auditors and the audit committee of registrant’sboard of directors (or persons performing the equivalent functions):

 

a. All significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonably likely to adverselyaffect the registrant’s ability to record, process, summarize and reportfinancial information; and

 

b. Any fraud, whether ornot material, that involves management or other employees who have asignificant role in the registrant’s internal control over financial reporting.

 

Date: November 14, 2007
| /s/ Christoph Westphal                                                       |   |   |
|------------------------------------------------------------------------------|--------|--------|
| Christoph Westphal                                                           |   |
| President and Chief Executive Officer

(principal executive officer)

  |   |

 

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