Exhibit 4b
                      MASTER REGISTRATION RIGHTS AGREEMENT

         MASTER REGISTRATION  RIGHTS AGREEMENT (this  "AGREEMENT"),  dated as of
August  6,  1997 by and  among  DYNAGEN,  INC.,  a  Delaware  corporation,  with
headquarters  located at 99 Erie  Street,  Cambridge,  Massachusetts  02139 (the
"COMPANY"),  and the undersigned parties who execute a counterpart  signature of
this Agreement (together with affiliates, the "INITIAL INVESTORS").

         WHEREAS:

         A. In connection  with the Securities  Purchase  Agreement of even date
herewith by and between the Company and the Initial  Investors (the  "SECURITIES
PURCHASE AGREEMENT"),  the Company has agreed, upon the terms and subject to the
conditions  contained therein, to issue and sell to the Initial Investors shares
of the  Company's  Series A Preferred  Stock (the  "PREFERRED  SHARES") that are
convertible into shares (collectively, the "CONVERSION SHARES") of the Company's
common  stock (the  "COMMON  STOCK")  and  Warrants  (the  "WARRANTS")  that are
exercisable  for shares of Common  Stock (the  "WARRANT  SHARES"),  all upon the
terms and subject to the limitations and conditions set forth in the Certificate
of Designation with respect to the Series A Preferred Stock or the Warrants,  as
applicable; and

         B.  To  induce  the  Initial  Investors  to  execute  and  deliver  the
Securities  Purchase  Agreement,  the  Company  has  agreed to  provide  certain
registration rights under the Securities Act of 1933, as amended,  and the rules
and regulations thereunder, or any similar successor statute (collectively,  the
"1933 ACT");

         NOW,  THEREFORE,  in  consideration  of the  premises  and  the  mutual
covenants  contained  herein  and other  good and  valuable  consideration,  the
receipt and  sufficiency of which are hereby  acknowledged,  the Company and the
Initial Investors hereby agree as follows:

         1.       DEFINITIONS.

                  (a) As used in this Agreement,  the following terms shall have
the following meanings:

                           (i) "CLOSING  DATE," with  respect to each  Investor,
means the date of the  consummation  of the  financing  in which  such  Investor
purchased debt or equity securities of the Company pursuant to which the Company
has granted registration rights.

                           (ii)  "INVESTORS"  means the Initial  Investors,  any
transferees  or assignees  who agree to become bound by the  provisions  of this
Agreement in accordance with Section 9 hereof and any party that becomes a party
to this Agreement in accordance with Section 10(b) hereof.

                           (iii) "REGISTER,"  "REGISTERED,"  and  "REGISTRATION"
refer  to a  registration  effected  by  preparing  and  filing  a  Registration
Statement or Statements in compliance with the





1933 Act and  pursuant  to Rule 415  under  the 1933 Act or any  successor  rule
providing for offering  securities on a continuous  basis ("RULE 415"),  and the
declaration or ordering of effectiveness of such  Registration  Statement by the
United States Securities and Exchange Commission (the "SEC").

                           (iv)  "POTENTIAL  MATERIAL  EVENT"  means  any of the
following:  (a) the possession by the Company of material  information  not ripe
for  disclosure  in a  registration  statement,  which  shall  be  evidenced  by
determinations  in good  faith by the Board of  Directors  of the  Company  that
disclosure  of  such  information  in  the   registration   statement  would  be
detrimental  to the  business  and affairs of the  Company;  or (b) any material
engagement  or  activity  by  the  Company  which  would,   in  the  good  faith
determination of the Board of Directors of the Company, be adversely affected by
disclosure in a registration  statement at such time, which  determination shall
be  accompanied by a good faith  determination  by the Board of Directors of the
Company that the registration  statement would be materially  misleading  absent
the inclusion of such information.

                           (v) "REGISTRABLE SECURITIES" means (i) the Conversion
Shares and the Warrant  Shares  issued or issuable,  (ii) shares of Common Stock
issued on a Closing  Date or  issuable  pursuant  to  securities  of the Company
issued on a Closing Date to an Investor that has signed a counterpart  signature
page to this Agreement  pursuant to Section 10(b) hereof and (iii) any shares of
capital  stock  issued  or  issuable  as a  dividend  on or in  exchange  for or
otherwise with respect to any of the foregoing.

                           (vi)  "REGISTRATION  STATEMENT"  means a registration
statement  of the  Company  under the 1933 Act or an  amendment  to an  existing
registration statement to add Registrable Securities.

                  (b)  Capitalized  terms used herein and not otherwise  defined
herein shall have the respective  meanings set forth in the Securities  Purchase
Agreement.

         2.       REGISTRATION.

                  (a)  Mandatory  Registration.  The Company  shall,  as soon as
practicable  after each Closing Date but in no event more than 45 days following
such Closing Date,  file with the SEC a Registration  Statement on Form S-3 (or,
if Form S-3 is not then available,  on such form of Registration Statement as is
then available to effect a registration of the Registrable  Securities,  subject
to the  consent of the  Investors  (as  determined  pursuant  to  Section  10(a)
hereof), which consent will not be unreasonably withheld conditioned or delayed)
covering  the resale of the  Registrable  Securities  issued or issuable to such
Investors  pursuant to  securities  of the Company  issued on each such  Closing
Date. The Registration Statement, to the extent allowable under the 1933 Act and
the Rules  promulgated  thereunder  (including Rule 416),  shall state that such
Registration  Statement  also covers  such  indeterminate  number of  additional
shares of Common Stock as may become  issuable upon  conversion of the Preferred
Shares and/or exercise of the Warrants to prevent dilution  resulting from stock
splits, stock dividends or similar transactions.  The Company shall use its best
efforts to cause such registration to become and remain effective


                                      -2-


(including  the taking of such steps as are  necessary  to obtain the removal of
any stop orders); provided, that the Investors shall furnish the Company, within
five (5) business days of the Company's  written request,  with such appropriate
information in connection  therewith  (whether  requested  prior to or after the
filing  of the  Registration  Statement  with  the  SEC)  as the  Company  shall
reasonably request in writing. The Registration Statement (and each amendment or
supplement thereto, and each request for acceleration of effectiveness  thereof)
shall be provided to (and subject to the approval  of) the  Investors  and their
counsel prior to its filing or other submission.  The number of shares of Common
Stock initially  included in such  Registration  Statement shall be no less than
one hundred  fifty  percent  (150%) of the shares of Common  Stock issued to the
Investors  on such Closing Date or issuable  pursuant to the  securities  of the
Company  issued to the Investors on such Closing Date  (assuming the  Conversion
Price set forth in Section  5(b)(ii)(A) of the Certificate of Designation).  The
Company  further  undertakes  to take  all  steps  necessary  to  ensure  that a
Registration  Statement is, or  Registration  Statements  are,  effective at all
times  during the  Registration  Period (as defined  below) with  respect to all
Registrable Securities and the resale thereof.

                  (b)  Eligibility  for Form S-3.  The  Company  represents  and
warrants that, as of the date hereof,  it meets the  requirements for the use of
Form  S-3 for  registration  of the  sale by the  Investors  of the  Registrable
Securities  and the Company  shall file all reports  required to be filed by the
Company with the SEC in a timely manner, and take any and all such other actions
as may be reasonably necessary or appropriate so as to maintain such eligibility
for the use of Form S-3.

         3.       OBLIGATIONS OF THE COMPANY.

         In connection with the registration of the Registrable Securities,  the
Company shall have the following obligations:

                  (a) The  Company  shall,  as soon as  practicable  after  each
Closing  Date but in no event more than 45 days  following  such  Closing  Date,
prepare and file promptly with the SEC a  Registration  Statement and thereafter
use its  Best  Efforts  (as  hereinafter  defined)  to cause  such  Registration
Statement relating to Registrable  Securities to promptly become effective,  but
in no event to become  effective  more than 90 days following such Closing Date,
and to keep the  Registration  Statement  effective  pursuant to Rule 415 at all
times  until  such  date as is the  earlier  of (i) the date on which all of the
Registrable  Securities  registered under such Registration  Statement have been
sold and no Preferred Shares, Warrants or other securities of the Company issued
on such  Closing  Date are  outstanding  or (ii)  the date on which  all of such
Registrable  Securities  (in the  opinion of counsel  to the  Investors)  may be
immediately  publicly  sold without  registration  and (iii) two years from such
Closing  Date  (the  "REGISTRATION   PERIOD"),   which  Registration   Statement
(including  any  amendments or supplements  thereto and  prospectuses  contained
therein and all documents  incorporated by reference  therein) shall not contain
any  untrue  statement  of a  material  fact or omit to  state a  material  fact
required to be stated therein,  or necessary to make the statements  therein not
misleading.  The Company  shall  furnish to the  Investors  copies of reasonably
complete drafts of all such documents proposed to be filed (including  exhibits,
if any),  and any such Investor  shall have the  opportunity  to object,  within


                                      -3-


three (3) business days, to any information  pertaining  solely to such Investor
that is contained  therein and the Company will make the corrections  reasonably
requested by such Investor with respect to such information  prior to filing any
such  Registration  Statement  or  amendment.  Any period of review and revision
resulting  from such review that extends  beyond five (5) business days shall be
added to the time in which  the  Registration  Statement  is to be filed  and no
penalty shall be assessed  with respect to such period.  If the Company fails to
cause such  Registration  Statement to become effective within 90 days following
the Closing Date due to a Corporation  Failure, as defined in the Certificate of
Designation, the Conversion Price, as defined in the Certificate of Designation,
shall  be  adjusted  as set  forth  in  paragraph  5(b)  of the  Certificate  of
Designation.  As used in Section 3(a), (b), (d), (f), (i) and (m) hereof,  "Best
Efforts"  shall  include  the  taking  of  any  and  all  actions  necessary  or
appropriate with respect thereto,  including timely response to all comments and
correspondence received (including from the SEC), the filing or providing of any
further drafts and other documents as may be required, and the like.

                  (b) The  Company  shall  prepare  and  file  with the SEC such
amendments  (including   post-effective   amendments)  and  supplements  to  the
Registration   Statement  and  the  prospectus   used  in  connection  with  the
Registration  Statement as may be necessary to keep the  Registration  Statement
effective at all times during the Registration  Period.  Without limiting any of
the  Company's  obligations  under  this  Agreement,  in the event the number of
shares available under a Registration Statement filed pursuant to this Agreement
is insufficient to cover all of the  Registrable  Securities  issued or issuable
upon  conversion of the Preferred  Shares and/or  exercise of the Warrants,  the
Company  shall  amend the  Registration  Statement,  or file a new  Registration
Statement (on the short form available therefore, if applicable), or both, so as
to  cover  all  of  the  Registrable  Securities,  in  each  case,  as  soon  as
practicable,  but in any  event  within  twenty  (20) days  after the  necessity
therefor  arises  (based  on the  market  price of the  Common  Stock  and other
relevant  factors on which the Company  reasonably  elects to rely). The Company
shall use its Best  Efforts to cause  such  amendment  and/or  new  Registration
Statement to become effective as soon as possible following the filing thereof.

                  (c)  The  Company  shall   furnish  to  each  Investor   whose
Registrable  Securities are included in the Registration Statement and its legal
counsel (i) promptly after the same is prepared and publicly distributed,  filed
with the SEC or received by the Company, one copy of the Registration  Statement
and any amendment thereto,  each preliminary  prospectus and prospectus and each
amendment or supplement thereto, and, in the case of the Registration  Statement
referred to in Section 2(a),  each letter written by or on behalf of the Company
to the SEC or the staff of the SEC,  and each  material  item of  correspondence
from the SEC or the staff of the SEC, in each case relating to such Registration
Statement  (other than any portion  thereof that contains  information for which
the Company has sought confidential  treatment),  and (ii) such number of copies
of a prospectus,  including a preliminary  prospectus,  and all  amendments  and
supplements  thereto and such other  documents as such  Investor may  reasonably
request in order to facilitate  the  disposition of the  Registrable  Securities
owned by such Investor.

                  (d) The Company shall use its Best Efforts to (i) register and
qualify the Registrable  Securities covered by the Registration  Statement under
such other  securities  or "blue sky" laws of such  jurisdictions  in the United
States as the  Investors  who hold a majority  in  interest


                                      -4-




of the Registrable Securities being offered reasonably request, (ii) prepare and
file  in  those   jurisdictions   such  amendments   (including   post-effective
amendments) and supplements to such  registrations and  qualifications as may be
necessary to maintain the effectiveness  thereof during the Registration Period,
(iii) take such other actions as may be necessary,  appropriate  or available to
maintain such registrations and qualifications in effect at all times during the
Registration  Period,  and (iv) take all other actions necessary or advisable to
qualify the  Registrable  Securities for sale in such  jurisdictions;  provided,
however,  that the Company shall not be required in connection therewith or as a
condition  thereto to (a) qualify to do business  in any  jurisdiction  where it
would not  otherwise  be  required  to qualify but for this  Section  3(d),  (b)
subject itself to general taxation in any such jurisdiction,  (c) file a general
consent  to  service  of  process  in any such  jurisdiction,  (d)  provide  any
undertakings  that cause the Company  undue  expense or burden,  or (e) make any
change in its charter or bylaws,  which in each case the Board of  Directors  of
the Company  determines to be contrary to the best  interests of the Company and
its  stockholders.  The Company  shall  promptly  notify each Investor who holds
Registrable  Securities of the receipt by the Company of any  notification  with
respect to the suspension of the  registration  or  qualification  of any of the
Registrable  Securities  for sale under the securities or "blue sky" laws of any
jurisdiction  in the  United  States  or its  receipt  of  actual  notice of the
initiation or threatening of any proceeding for such purpose.

                  (e) Notwithstanding the foregoing, if at any time or from time
to time  after the date of  effectiveness  of the  Registration  Statement,  the
Company  notifies  the  Investors  in writing of the  existence  of a  Potential
Material Event, the Investors shall not offer or sell any Registrable Shares, or
engage in any other transaction involving or relating to the Registrable Shares,
from the time of the giving of notice with respect to a Potential Material Event
until the  earlier  of (i) twenty  (20) days from the  receipt of notice of such
Potential Material Event, or (ii) such Investor receives written notice from the
Company that such  Potential  Material  Event  either has been  disclosed to the
public or no longer constitutes a Potential Material Event;  provided,  however,
that the Company shall use its best efforts to minimize any such  suspension and
under all circumstances the Company may not so suspend the right to such holders
of Registrable  Shares for more than two periods of twenty (20) days each in the
aggregate  during  any  12-month  period  during  the  period  the  Registration
Statement is required to be in effect; and provided,  further,  that there shall
be an interval of no less than 45 days between such two twenty (20) day periods.

                  (f) The  Company  shall use its Best  Efforts to  prevent  the
issuance  of  any  stop  order  or  other   suspension  of  effectiveness  of  a
Registration  Statement,  and,  if  such an  order  is  issued,  to  obtain  the
withdrawal  of such order at the  earliest  possible  moment and to notify  each
Investor  who holds  Registrable  Securities  being sold (or, in the event of an
underwritten  offering, the managing underwriters) of the issuance of such order
and the resolution thereof.

                  (g) For a period  of five (5)  business  days  prior to filing
with the SEC, the Company  shall permit a single firm of counsel  designated  by
the Investors  representing a majority of the Registrable Securities held by the
Investors (on an as converted and as exercised basis) to review the Registration
Statement and all amendments and supplements  thereto.  Any period of review and
revision  resulting  from any such review that extends  beyond five (5) business
days


                                      -5-



shall be added to the time in which  registration  is  required  to be filed and
effective, as appropriate, and no penalty shall be assessed with respect to such
period.

                  (h) The Company shall make available for inspection by (i) any
Investor, (ii) any underwriter  participating in any disposition pursuant to the
Registration Statement,  (iii) one firm of attorneys and one firm of accountants
or other  agents  retained  by the  Investors,  and  (iv) one firm of  attorneys
retained by all such underwriters (collectively, the "INSPECTORS") all pertinent
financial and other records, and pertinent corporate documents and properties of
the  Company  (collectively,  the  "RECORDS")  as  shall  be  reasonably  deemed
necessary  by each  Inspector  to enable  each  Inspector  to  exercise  its due
diligence  responsibility,  and  cause the  Company's  officers,  directors  and
employees to supply all information  which any Inspector may reasonably  request
for purposes of such due diligence; provided, however, that each Inspector shall
hold in  confidence  and shall not make any  disclosure  of any  Record or other
information which the Company  determines in good faith to be confidential,  and
of which determination the Inspectors are so notified, unless (a) the disclosure
of such Records is  determined  to be necessary by the Investors and the Company
to avoid or correct a misstatement  or omission in any  Registration  Statement,
(b) the release of such Records is ordered pursuant to a subpoena or other order
from  a  court  or  government  body  of  competent  jurisdiction,  or  (c)  the
information  in such  Records has been made  generally  available  to the public
other  than by  disclosure  in  violation  of this or any other  agreement.  The
Company shall not be required to disclose any  confidential  information in such
Records to any Inspector until and unless such Inspector shall have entered into
confidentiality  agreements (in form and substance  satisfactory to the Company)
with the Company with respect thereto, containing terms substantially similar to
those contained in this Section 3(i).  Each Investor agrees that it shall,  upon
learning  that  disclosure  of  such  Records  is  sought  in or by a  court  or
governmental body of competent  jurisdiction or through other means, give prompt
notice to the  Company  and allow the  Company,  at its  expense,  to  undertake
appropriate  action to prevent  disclosure  of, or to obtain a protective  order
for, the Records  deemed  confidential.  Nothing herein shall be deemed to limit
the  Investor's  ability to sell  Registrable  Securities  in a manner  which is
otherwise consistent with applicable laws and regulations.

                  (i) The  Company  shall  hold in  confidence  and not make any
disclosure of information  concerning an Investor provided to the Company unless
(i) disclosure of such  information is necessary to comply with federal or state
securities   laws,  or  other  applicable  law,  (ii)  the  disclosure  of  such
information is necessary to avoid or correct a  misstatement  or omission in any
Registration  Statement,  (iii)  the  release  of such  information  is  ordered
pursuant  to a  subpoena  or other  order from a court or  governmental  body of
competent  jurisdiction,  or (iv)  such  information  has  been  made  generally
available  to the public  other than by  disclosure  in violation of this or any
other agreement. The Company agrees that it shall, upon learning that disclosure
of such  information  concerning  an  Investor  is  sought  in or by a court  or
governmental body of competent  jurisdiction or through other means, give prompt
notice to such Investor prior to making such disclosure, and allow the Investor,
at its expense, to undertake  appropriate action to prevent disclosure of, or to
obtain a protective order for, such information.

                  (j) The  Company  shall use its Best  Efforts  to  secure  the
designation  and  quotation  of all the  Registrable  Securities  covered by the
Registration  Statement on the NASDAQ 


                                      -6-



SmallCap Market, if the listing of such Registrable Securities is then permitted
under the rules and regulations of such market.

                  (k) The Company shall provide a transfer  agent and registrar,
which may be a single  entity,  for the  Registrable  Securities  not later than
sixty (60) days from the Closing Date.

                  (l)  The  Company  shall   promptly   facilitate   the  timely
preparation and delivery of certificates  (not bearing any restrictive  legends)
representing  Registrable  Securities  to be sold  pursuant to the  Registration
Statement and enable such  certificates to be in such  denominations or amounts,
as the case may be, as the managing underwriter or underwriters,  if any, or the
Investors may  reasonably  request and  registered in such names as the managing
underwriter or underwriters, if any, or the Investors may request.

                  (m) The  Company  shall  use its Best  Efforts  to  cause  all
Registrable  Securities covered by such registration  statement to be registered
with or approved by such other  governmental  agencies or  authorities as may be
necessary to enable each holder thereof to consummate disposition of Registrable
Securities.

         4.       OBLIGATIONS OF THE INVESTORS.

         In connection with the registration of the Registrable Securities,  the
Investors shall have the following obligations:

                  (a) It shall be a condition  precedent to the  obligations  of
the Company to complete the registration pursuant to this Agreement with respect
to the Registrable  Securities of a particular Investor that such Investor shall
furnish to the Company,  within five (5) business days of the Company's  written
request, such information  regarding itself, the Registrable  Securities held by
it and the intended method of disposition of the Registrable  Securities held by
it  as  shall  be  reasonably  required  to  effect  the  registration  of  such
Registrable  Securities  and shall  execute  within  five (5)  business  days of
receipt by such Investor such documents in connection with such  registration as
the Company may reasonably request.

                  (b)  Each  Investor,  by  such  Investor's  acceptance  of the
Registrable  Securities,  agrees to  cooperate  with the  Company as  reasonably
requested by the Company in connection  with the  preparation  and filing of the
Registration Statement hereunder,  unless such Investor has notified the Company
in  writing  of such  Investor's  election  to  exclude  all of such  Investor's
Registrable Securities from the Registration Statement.

                  (c) Each Investor agrees that, upon receipt of any notice from
the  Company of the  happening  of a  Potential  Material  Event as set forth in
Section  3(e),  such  Investor  will  immediately   discontinue  disposition  of
Registrable  Securities  pursuant to the  Registration  Statement  covering such
Registrable Securities in accordance with Section 3(e).

                  (d) Without limiting an Investor's  rights under Section 2(a),
no Investor may participate in any  underwritten  distribution  hereunder unless
such Investor (i) agrees to sell such


                                      -7-



Investor's  Registrable  Securities  on the basis  provided in any  underwriting
arrangements  in usual and  customary  form entered  into by the  Company,  (ii)
completes  and executes  all  questionnaires,  powers of attorney,  indemnities,
underwriting  agreements and other documents reasonably required under the terms
of such underwriting arrangements, and (iii) agrees to pay its pro rata share of
all  underwriting  discounts and commissions and any expenses in excess of those
payable by the Company pursuant to Section 5 below.

                  (e) Each Investor whose Registrable Securities are included in
a Registration Statement understands that the 1933 Act may require delivery of a
prospectus relating thereto in connection with any sale thereof pursuant to such
Registration  Statement and each such  Investor  shall use its  reasonable  best
efforts to comply with the applicable  prospectus  delivery  requirements of the
1933 Act in connection with any such sale.

                  (f) Each Investor agrees to notify the Company  promptly,  but
in any  event  within  seventy-two  (72)  hours  after  the  date on  which  all
Registrable  Securities  owned by such Investor have been sold by such Investor,
so that the Company may comply with its obligation to terminate the Registration
Statement in accordance  with Item 512 of Regulation  S-K or Regulation  S-B, as
the case may be.

         5.       EXPENSES OF REGISTRATION.

         All  reasonable  expenses,   other  than  underwriting   discounts  and
commissions,   incurred   in   connection   with   registrations,   filings   or
qualifications pursuant to Sections 2 and 3, including all registration, listing
and  qualifications  fees,  printers  and  accounting  fees  and  the  fees  and
disbursements  of counsel for the Company,  shall be borne by the  Company.  All
fees and disbursements of counsel to the holders of Registrable Securities,  any
expenses incurred as a result of any investigation pursuant to Section 3(h), any
underwriting  discounts and  commissions  and all other expenses of such holders
not  contained  in the  previous  sentence  shall  be borne  by the  holders  of
Registrable Securities.

         6.       INDEMNIFICATION.

         In the event any Registrable  Securities are included in a Registration
Statement under this Agreement:

                  (a)  To  the  extent   permitted  by  law,  the  Company  will
indemnify,  hold  harmless  and  defend  (i) each  Investor  who is a seller  of
Registrable Securities under the Registration Statement, and (ii) the directors,
officers,  partners,  employees,  agents and each person who  controls  any such
Investor  within the meaning of the 1933 Act or the  Securities  Exchange Act of
1934, as amended (the "1934 ACT"),  if any,  (each,  an  "INDEMNIFIED  PERSON"),
against any joint or several losses,  claims,  damages,  liabilities or expenses
(collectively, together with actions, proceedings or inquiries by any regulatory
or  self-regulatory  organization,  whether commenced or threatened,  in respect
thereof,  "CLAIMS") to which any of them may become  subject under the 1933 Act,
the 1934 Act or  otherwise,  insofar as any such Claim arises out of or is based
upon: (i) any untrue statement or alleged untrue statement of a material fact in
a Registration  Statement or



                                      -8-


the omission or alleged omission to state therein a material fact required to be
stated or necessary to make the  statements  therein not  misleading or (ii) any
untrue statement or alleged untrue statement of a material fact contained in any
preliminary  prospectus if used prior to the effective date of such Registration
Statement, or contained in the final prospectus (as amended or supplemented,  if
the Company files any amendment  thereof or supplement  thereto with the SEC) or
the omission or alleged omission to state therein any material fact necessary to
make the statements made therein,  in light of the circumstances under which the
statements  therein were made,  not  misleading  (the  matters in the  foregoing
clauses  (i)  and  (ii)  being,  collectively,  "VIOLATIONS").  Subject  to  the
restrictions  set forth in  Section  6(c) with  respect  to the  number of legal
counsel,  the Company shall reimburse the Investors and each such underwriter or
controlling  person,  promptly as such  expenses  are  incurred  and are due and
payable,  for any reasonable legal fees or other reasonable expenses incurred by
them  in   connection   with   investigating   or  defending   any  such  Claim.
Notwithstanding  anything to the contrary contained herein, the  indemnification
agreement contained in this Section 6(a): (i) shall not apply to a Claim arising
out of or based upon a Violation which occurs in reliance upon and in conformity
with information  furnished in writing to the Company by any Indemnified  Person
expressly  for  use in  connection  with  the  preparation  of the  Registration
Statement,  preliminary prospectus or final prospectus, or any amendment thereof
or supplement thereto; (ii) shall not apply to amounts paid in settlement of any
Claim if such  settlement is effected  without the prior written  consent of the
Company,  which  consent  shall not be  unreasonably  withheld;  and (iii)  with
respect to any  preliminary  prospectus,  shall not inure to the  benefit of any
Indemnified  Person  if the  untrue  statement  or  omission  of  material  fact
contained in the  preliminary  prospectus was corrected on a timely basis in the
prospectus,  as then amended or supplemented,  if such corrected  prospectus was
timely made  available  by the Company  pursuant to Section  3(c)  hereof.  Such
indemnity shall remain in full force and effect  regardless of any investigation
made by or on behalf of the Indemnified Person and shall survive the transfer of
the   Registrable   Securities   by  the   Investors   pursuant  to  Section  9.
Notwithstanding  anything to the contrary  contained  herein,  any Investor that
does not fulfill its obligations under Sections 2(a), 3(a) or 4(a) hereof within
the period of time specified in such Sections shall not be an Indemnified Person
and shall not be entitled to indemnification pursuant to this Section 6.

                  (b) In connection with any Registration  Statement in which an
Investor is  participating,  each such Investor agrees severally and not jointly
to  indemnify,  hold  harmless  and  defend,  to the same extent and in the same
manner set forth in Section 6(a), the Company,  each of its  directors,  each of
its  officers who signs the  Registration  Statement,  each person,  if any, who
controls the Company within the meaning of the 1933 Act or the 1934 Act, and any
other stockholder selling securities  pursuant to the Registration  Statement or
any of its  directors  or officers or any person who controls  such  stockholder
within  the  meaning  of  the  1933  Act  or  the  1934  Act  (collectively,  an
"INDEMNIFIED PARTY"), against any Claim to which any of them may become subject,
under the 1933 Act, the 1934 Act or otherwise,  insofar as such Claim arises out
of or is based upon any  Violation,  in each case to the extent (and only to the
extent)  that such  Violation  occurs in reliance  upon and in  conformity  with
written information  furnished to the Company by such Investor expressly for use
in connection with such Registration Statement,  preliminary prospectus or final
prospectus,  or any amendment or supplement thereto; and subject to Section 6(c)
such  Investor  will  reimburse  any legal or other  expenses  (promptly as such



                                      -9-



expenses are incurred  and are due and payable)  reasonably  incurred by them in
connection with  investigating or defending any such Claim;  provided,  however,
that the indemnity  agreement  contained in this Section 6(b) shall not apply to
amounts paid in settlement of any Claim if such  settlement is effected  without
the  prior  written  consent  of  such  Investor,  which  consent  shall  not be
unreasonably withheld;  provided,  further,  however, that the Investor shall be
liable under this Agreement (including this Section 6(b) and Section 7) for only
that amount as does not exceed the net proceeds to such  Investor as a result of
the sale of Registrable Securities pursuant to such Registration Statement. Such
indemnity shall remain in full force and effect  regardless of any investigation
made by or on behalf of such Indemnified Party and shall survive the transfer of
the   Registrable   Securities   by  the   Investors   pursuant  to  Section  9.
Notwithstanding  anything to the contrary contained herein, the  indemnification
agreement  contained  in this  Section  6(b)  with  respect  to any  preliminary
prospectus shall not inure to the benefit of any Indemnified Party if the untrue
statement or omission of material fact contained in the  preliminary  prospectus
was  corrected  on a  timely  basis  in  the  prospectus,  as  then  amended  or
supplemented.

                  (c)  Promptly  after  receipt  by  an  Indemnified  Person  or
Indemnified  Party  under this  Section 6 of notice of the  commencement  of any
action  (including  any  governmental   action),   such  Indemnified  Person  or
Indemnified Party shall, if a Claim in respect thereof is to be made against any
indemnifying  party under this  Section 6, deliver to the  indemnifying  party a
written notice of the commencement  thereof,  and the  indemnifying  party shall
have the right to participate in, and, to the extent the  indemnifying  party so
desires,  jointly with any other indemnifying party similarly noticed, to assume
control  of the  defense  thereof  with  counsel  mutually  satisfactory  to the
indemnifying  party and the Indemnified  Person or the Indemnified Party, as the
case may be; provided,  however, that an Indemnified Person or Indemnified Party
shall have the right to retain its own counsel  with the fees and expenses to be
paid by the  indemnifying  party,  if,  in the  reasonable  opinion  of  counsel
retained by the indemnifying  party, the  representation  by such counsel of the
Indemnified  Person or  Indemnified  Party and the  indemnifying  party would be
inappropriate  due to actual  or  potential  differing  interests  between  such
Indemnified  Person or Indemnified Party and any other party represented by such
counsel  in such  proceeding.  The  indemnifying  party  shall  pay for only one
separate legal counsel for the Indemnified  Persons or the Indemnified  Parties,
as applicable,  and such legal counsel shall be selected by Investors  holding a
majority-in-interest  of the Registrable Securities included in the Registration
Statement  to  which  the  Claim  relates,  if the  Investors  are  entitled  to
indemnification  hereunder,  or the  Company,  if the  Company  is  entitled  to
indemnification  hereunder, as applicable. The failure to deliver written notice
to the  indemnifying  party within a reasonable time of the  commencement of any
such action shall not relieve such  indemnifying  party of any  liability to the
Indemnified  Person or  Indemnified  Party  under this  Section 6, except to the
extent  that the  indemnifying  party is actually  prejudiced  in its ability to
defend such action. The indemnification required by this Section 6 shall be made
by  periodic   payments  of  the  amount   thereof  during  the  course  of  the
investigation or defense, as such expense, loss, damage or liability is incurred
and is due and payable.

         7.       CONTRIBUTION.

         To  the  extent  any   indemnification  by  an  indemnifying  party  is
prohibited or limited by law, the indemnifying  party agrees to make the maximum
contribution  with respect to any amounts for


                                      -10-



which it would  otherwise  be  liable  under  Section  6 to the  fullest  extent
permitted by law;  provided,  however,  that (i) no  contribution  shall be made
under   circumstances   where  the  maker   would  not  have  been   liable  for
indemnification under the fault standards set forth in Section 6, (ii) no seller
of Registrable  Securities  guilty of fraudulent  misrepresentation  (within the
meaning of Section 11(f) of the 1933 Act) shall be entitled to contribution from
any person who was not guilty of such  fraudulent  misrepresentation,  and (iii)
contribution  (together with any indemnification or other obligations under this
Agreement) by any seller of Registrable Securities shall be limited in amount to
the amount of proceeds received by such seller from the sale of such Registrable
Securities.

         8.       REPORTS UNDER THE 1934 ACT.

         With a view to making  available to the  Investors the benefits of Rule
144  promulgated  under the 1933 Act or any other  similar rule or regulation of
the SEC that may at any time  permit the  Investors  to sell  securities  of the
Company to the public without registration ("RULE 144"), the Company agrees to:

                  (a) make and keep public information available, as those terms
are understood and defined in Rule 144;

                  (b) file with the SEC in a timely manner all reports and other
documents required of the Company under the 1933 Act and the 1934 Act so long as
the filing of such  reports and other  documents is required for the sale of the
Registrable Securities pursuant to Rule 144; and

                  (c)  furnish to each  Investor so long as such  Investor  owns
Registrable  Securities,  promptly upon request,  (i) a written statement by the
Company that it has complied  with the reporting  requirements  of Rule 144, the
1933 Act and the 1934 Act,  (ii) a copy of the most recent  annual or  quarterly
report of the  Company  and such other  reports  and  documents  so filed by the
Company,  and (iii) such other  information  as may be  reasonably  requested to
permit  the  Investors  to sell such  securities  pursuant  to Rule 144  without
registration.

         9.       ASSIGNMENT OF REGISTRATION RIGHTS.

         The rights of an Investor  hereunder,  including  the right to have the
Company register  Registrable  Securities  pursuant to this Agreement,  shall be
automatically  assignable by each Investor to any  transferee of at least 30% of
the Preferred Shares and/or Warrants, or Registrable Securities of such Investor
if (i) the Investor  agrees in writing with the transferee or assignee to assign
such rights,  and a copy of such  agreement is furnished to the Company within a
reasonable time after such assignment,  (ii) the Company is, within a reasonable
time after such transfer or assignment, furnished with written notice of (a) the
name and address of such  transferee or assignee,  and (b) the  securities  with
respect to which such  registration  rights are being  transferred  or assigned,
(iii)  following  such transfer or assignment,  the further  disposition of such
securities by the  transferee  or assignee is restricted  under the 1933 Act and
applicable  state  securities  laws,  (iv) at or  before  the time  the  Company
receives the written notice  contemplated  by clause (ii) of


                                      -11-


this sentence,  the transferee or assignee agrees in writing with the Company to
be bound by all of the provisions contained herein, (v) such transfer shall have
been made in  accordance  with the  applicable  requirements  of the  Securities
Purchase Agreement,  and (vi) such transferee shall be an "accredited  investor"
as that term defined in Rule 501 of Regulation D promulgated under the 1933 Act.

         10.      AMENDMENT OF REGISTRATION RIGHTS.

                  (a)  Provisions  of  this  Agreement  may be  amended  and the
observance  thereof may be waived (either generally or in a particular  instance
and either  retroactively  or  prospectively),  only with written consent of the
Company and Investors who hold at least 80% of the Registrable  Securities.  Any
amendment or waiver effected in accordance with this Section 10 shall be binding
upon each Investor and the Company.

                  (b)  Notwithstanding  the foregoing,  the Company may, without
the  consent of the  existing  Investors,  amend this  Agreement  at any time to
include  additional  parties so long as the Company and such additional  parties
execute a counterpart  signature page to this Agreement.  When this Agreement is
so amended,  such additional parties shall be "Investors" hereunder and shall be
entitled to all benefits and bound by all obligations hereunder.

         11.      MISCELLANEOUS.

                  (a) A person or entity is deemed to be a holder of Registrable
Securities  whenever  such  person or entity  owns of  record  such  Registrable
Securities.  If  the  Company  receives  conflicting  instructions,  notices  or
elections  from  two or more  persons  or  entities  with  respect  to the  same
Registrable  Securities,  the Company shall act upon the basis of  instructions,
notice  or  election  received  from the  registered  owner of such  Registrable
Securities.

                  (b) Notices  required or permitted to be given hereunder shall
be in  writing  and shall be deemed to be  sufficiently  given  when  personally
delivered (by hand, by courier,  by telephone  line  facsimile  transmission  or
other means) or sent by facsimile or overnight courier,

         If to the Company, to:

                  DynaGen, Inc.
                  99 Erie Street
                  Cambridge, MA  02139
                  Attention:  President

                  Telephone:        (617) 491-2527
                  Telecopy:         (617) 354-3902

if to the  Investors  as set forth in the  subscription  agreements  pursuant to
which the  Investors  purchased  securities  of the  Company,  or at such  other
address as each such party  furnishes  by 


                                      -12-


notice given in accordance with this Section 11(b), and shall be effective, when
personally  delivered,  upon receipt and, when so sent by facsimile or overnight
courier.

                  (c) Failure of any party to exercise any right or remedy under
this  Agreement or otherwise,  or delay by a party in  exercising  such right or
remedy, shall not operate as a waiver thereof

                  (d)  This  Agreement  shall  be  enforced,   governed  by  and
construed in  accordance  with the laws of the State of Delaware  applicable  to
agreements  made and to be performed  entirely  within such State.  In the event
that any  provision  of this  Agreement  is invalid or  unenforceable  under any
applicable  statute  or  rule  of law,  then  such  provision  shall  be  deemed
inoperative  to the extent that it may  conflict  therewith  and shall be deemed
modified to conform with such statute or rule of law. Any provision hereof which
may prove invalid or  unenforceable  under any law shall not affect the validity
or enforceability of any other provision hereof. Each of the parties consents to
the jurisdiction of the federal courts whose districts encompass any part of the
City of New York or the state  courts of the  State of New York  sitting  in the
City of New York in connection with any dispute arising under this Agreement and
hereby waives, to the maximum extent permitted by law, any objection,  including
any  objection  based on  forum  non  conveniens,  to the  bringing  of any such
proceeding in such jurisdictions.

                  (e) This Agreement and the subscription agreements pursuant to
which the Investors purchased securities of the Company (including all schedules
and exhibits  thereto)  constitute the entire agreement among the parties hereto
with  respect  to  the  subject   matter  hereof  and  thereof.   There  are  no
restrictions,  promises, warranties or undertakings,  other than those set forth
or  referred  to  herein  and  therein.  This  Agreement  and such  subscription
agreements  supersede all prior agreements and understandings  among the parties
hereto with respect to the subject matter hereof and thereof.

                  (f)  Subject to the  requirements  of  Section 9 hereof,  this
Agreement  shall inure to the benefit of and be binding upon the  successors and
assigns of each of the parties hereto.

                  (g) The  headings in this  Agreement  are for  convenience  of
reference only and shall not limit or otherwise affect the meaning hereof.

                  (h)  This   Agreement   may  be   executed   in  two  or  more
counterparts,  each of which shall be deemed an original  but all of which shall
constitute one and the same agreement. This Agreement, once executed by a party,
may be delivered to the other party hereto by facsimile  transmission  of a copy
of this  Agreement  bearing  the  signature  of the  party  so  delivering  this
Agreement.

                  (i) Each party shall do and  perform,  or cause to be done and
performed,  all such further acts and things,  and shall execute and deliver all
such other  agreements,  certificates,  instruments and documents,  as the other
party may reasonably request in order to carry out the intent and accomplish the
purposes of this Agreement and the consummation of the transactions contemplated
hereby.


                                      -13-



                  (j) All  consents and other  determinations  to be made by the
Investors  pursuant to this Agreement  shall be made by the Investors  holding a
majority of the Registrable  Securities  (determined as if all Preferred  Shares
and Warrants then  outstanding  had been  converted or exercised,  respectively,
into Registrable Securities).

                [REMAINDER OF PAGE IS INTENTIONALLY LEFT BLANK.]




                                      -14-





                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                     Very truly yours,

                                                     DYNAGEN, INC.

                                                     By:     /s/ Indu A. Muni
                                                        ------------------------
                                                     Title:  President
                                                           ---------------------






                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                              Very truly yours,

                                              Arab Commerce Bank, Ltd.
                                              ----------------------------------
                                              (print exact name of Investor)

                                              By:      [illegible]
                                                 -------------------------------

                                              Title:   Co. Secretary
                                                    ----------------------------





                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Swedbank Luxembourg
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      [illegible]
                                                    ----------------------------

                                                 Title:   Senior Account Manager
                                                       -------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Paul Enquist
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ Paul Enquist
                                                    ----------------------------

                                                 Title:
                                                       -------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                  Very truly yours,

                                                  Leo Genecco & Sons Inc.
                                                  ------------------------------
                                                  (print exact name of Investor)

                                                  By:      /s/ David L. Genecco
                                                     ---------------------------

                                                  Title:   President
                                                        ------------------------










                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 William S. Kissel
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ William S. Kissel
                                                    ----------------------------

                                                 Title:
                                                       -------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Irving Schotz
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ Irving Schotz
                                                    ----------------------------

                                                 Title:
                                                       -------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Dick Alaimo, Jr.
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ Dick Alaimo, Jr.
                                                    ----------------------------

                                                 Title:
                                                       -------------------------









                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                  Very truly yours,

                                                  Jon A. Travers
                                                  ------------------------------
                                                  (print exact name of Investor)

                                                  By:      /s/ Jon A. Travers
                                                     ---------------------------

                                                  Title:
                                                        ------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                Very truly yours,

                                                C. Robert Cusick
                                                -------------------------------
                                                (print exact name of Investor)

                                                By:      /s/ C. Robert Cusick
                                                   -----------------------------

                                                Title:
                                                      --------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                  Very truly yours,

                                                  Robert C. Cohen
                                                  ------------------------------
                                                  (print exact name of Investor)

                                                  By:      /s/ Robert C. Cohen
                                                     ---------------------------

                                                  Title:
                                                        ------------------------








                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Christopher Grieco
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ Christopher Grieco
                                                    ----------------------------

                                                 Title:
                                                       -------------------------









                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 Richard and Ronda Tennis
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ Richard Tennis
                                                    ----------------------------

                                                 Title:
                                                       -------------------------







                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                Very truly yours,

                                                Robert D. Frankel
                                                --------------------------------
                                                (print exact name of Investor)

                                                By:      /s/ Robert D. Frankel
                                                   -----------------------------

                                                Title:
                                                      --------------------------







                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                             Very truly yours,

                                             A. Ronald Jacobstein
                                             -----------------------------------
                                             (print exact name of Investor)

                                             By:      /s/ A. Ronald Jacobstein
                                                 -------------------------------

                                             Title:
                                                   -----------------------------







                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                                 Very truly yours,

                                                 J. Michael Nixon
                                                 -------------------------------
                                                 (print exact name of Investor)

                                                 By:      /s/ J. Michael Nixon
                                                    ----------------------------

                                                 Title:
                                                       -------------------------






                                  DYNAGEN, INC.

                      MASTER REGISTRATION RIGHTS AGREEMENT

                           Counterpart Signature Page


         If you are in  agreement  with the  foregoing,  please sign the form of
acceptance on the enclosed  counterpart of this Agreement and return the same to
the Company,  whereupon,  this Agreement shall become a binding  Agreement among
us.

                                      Very truly yours,

                                      Guarantee & Trust Co. FBO J. Thomas Chess
                                      ------------------------------------------
                                      (print exact name of Investor)

                                      By:      /s/ J. Thomas Chess
                                         ---------------------------------------

                                      Title:
                                            ------------------------------------