13G Filing: Eastern Capital Ltd and Synlogic Inc. (SYBX)

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G/A

Under the Securities Exchange
Act of 1934
(Amendment No. 1)*

Synlogic, Inc.

(Name of Issuer)

COMMON STOCK, $0.001
PAR VALUE PER SHARE

(Title of Class of Securities)

87166L100

(CUSIP Number)

William Sullivan,
10 Market Street, #773 Camana Bay Grand Cayman, KY1-9006 CAYMAN ISLANDS, 345-640-3330

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

August 28, 2017

(Date of Event which Requires Filing of this
Statement)

Check
the appropriate box to designate the rule pursuant to which this Schedule is filed:
¨  Rule 13d-1(b)
☒  Rule
13d-1(c)
¨  Rule 13d-1(d)

^* The remainder of
this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities,
and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the
remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange
Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other
provisions of the Act (however, see the Notes).

Item 1.

Item 2.

Item 3.  If this statement is filed pursuant
to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

Item 4.  Ownership.

Provide the following information regarding the aggregate
number and percentage of the class of securities of the issuer identified in Item 1.

The percentage ownership noted
in this Schedule 13G is based on 16,282,496 shares outstanding as of August 28, 2017 as reported in the Issuer’s Form 8K
filed with the U.S. Securities and Exchange Commission on August 28, 2017.

As of the date of this filing, Eastern Capital Limited, Portfolio Services
Ltd. and Mr. Dart beneficially own in aggregate the following:

Instruction. For computations regarding securities
which represent a right to acquire an underlying security see §240.13d-3(d)(1).

Item 5.  Ownership of Five Percent or
Less of a Class.

If
this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial
owner of more than five percent of the class of securities, check the following     x.

Instruction. Dissolution of a group requires
a response to this item.

Item 6.  Ownership of More than Five Percent
on Behalf of Another Person.

Not Applicable

Item 7.  Identification and Classification
of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company.

Not Applicable

Item 8.  Identification and Classification
of Members of the Group.

Not Applicable

Item 9.  Notice of Dissolution of Group.

Not Applicable

Item 10.  Certification.

After reasonable inquiry and to the best of my knowledge
and belief, I certify that the information set forth in this statement is true, complete and correct.