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                                                                     Exhibit 4g

                            5% SECURED NON-NEGOTIABLE
                        LIMITED RECOURSE PROMISSORY NOTE


$200,000                                                  Boston, Massachusetts
                                                          May 13, 1998


         On August 12, 1998 (the "Maturity Date"), for value received, the
undersigned DynaGen, Inc., a Delaware corporation (the "Maker"), promises to pay
to Sovereign Partners, 90 Grove Street, Richfield, Connecticut 06877 (the
"Payee"), the principal sum of Two Hundred Thousand United States Dollars
($200,000) or the then outstanding principal amount hereof, together with
interest on any and all principal amounts remaining unpaid hereunder from time
to time outstanding from the date hereof until payment in full, such interest to
be payable at such rates and such times as are hereinafter specified. This Note
is a limited recourse note and payment is subject to the provisions of Section 2
hereof.

1.       INTEREST AND PRINCIPAL

         1.01     Interest. The Maker shall pay interest on the outstanding
principal amount of this Note from the date hereof until such principal amount
is paid in full at the rate of five percent (5%) per annum. Interest payments
shall be made on the maturity date. Any overdue installment of interest or
principal shall bear interest at the rate of Ten percent (10%) per annum.
Interest shall be calculated on the basis of a 365 day year for the actual
number of days elapsed.

         1.02     Exchange. The entire outstanding principal together with 
interest accrued thereon on the principal amount of this Note may be exchanged
by the Payee for a like face amount of shares of the Maker's Series D Preferred
Stock, $.01 par value per share ("Preferred Stock"), any time after the Maturity
Date.

         1.03     Optional Prepayment. This Note may be prepaid in whole or in 
part, at any time or from time to time before the Maturity Date, at the option
of the Maker, by paying to the Payee an amount equal to the amount to be prepaid
together a premium (which shall be inclusive of interest) of $25,000 if prepaid
within thirty (30) days after the date hereof or $37,500 if prepaid after 30
days after the date hereof and before 60 days after the date hereof or $50,000
if prepaid after 60 days after the date hereof and before the Maturity Date. In
the event that this Note shall be prepaid in part the premium (which shall be
inclusive of interest) shall be prorated.

         1.04     Mandatory Prepayment. This Note shall be prepaid together with
the premiums set forth in Section 1.03 (which shall be inclusive of interest),
to the extent possible, from the 
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proceeds (net of transaction, legal, accounting and related cost), if any, of
any private placement financing that is closed on or before the Maturity Date.

         1.05     Delivery of Payment. All payments made hereunder shall be made
by check mailed first class, postage paid to the Payee at the address set forth
above or to such other address as the Payee may from time to time designate in
writing to the Maker. Such payments shall be accompanied by a notice setting
forth in reasonable detail (a) the amount of interest and principal being paid
and (b) the remaining principal amount. If any payments are required to be made
on a day which is not a Business Day (as hereinafter defined) the date on which
such payment is required to be made shall be extended to, and such payment shall
be required to be made on, the next Business Day. "Business Day" shall mean a
day other than Saturday, Sunday and any day which shall be in the City of
Boston, Massachusetts, a legal holiday or a day on which banking institutions
are authorized by law to close.

2.       AGREEMENTS

         2.01     Security. Messrs. Dhanajay Wadekar and Indu Muni, stockholders
of the Maker, hereby grant to the Payee a pledge in the following described
property, to wit: 200,000 shares (the "Pledged Shares") of the common stock,
$.01 par value per share, of the Maker.

         2.02     Limited Recourse. The Payee hereby agrees that its sole 
recourse for Maker's failure to pay this Note shall be to either (i) exchange
this Note for shares of Preferred Stock in accordance with Section 1.02 or (ii)
to foreclose on the Pledged Shares in accordance with Section 2.01.

3.       SUBORDINATION

         3.01     Subordinated Debt. The indebtedness evidenced by this 
instrument ("Subordinated Debt") is subordinate and junior in right of payment,
to the extent and in the manner set forth below, to all Superior Debt (as
defined in SECTION 3.02 ) of the Maker to the extent provided in this section.

         3.02     Superior Debt. For the purpose of these subordination 
provisions the term "Superior Debt" shall mean all principal, interest, charges,
expenses, and attorneys' fees arising out of or relating to all indebtedness of
Maker or any subsidiary of Maker owing to any institutional lender including,
without limitation, Fleet Bank, Sirrom Capital Corporation, and The Huntington
National Bank (each, a "Bank") whether outstanding on the date of this Note or
subsequently incurred to renew, extend, modify or otherwise amend the Superior
Debt unless under the instrument evidencing the same or under which the same is
outstanding, it is expressly provided that such indebtedness is junior and
subordinate to other indebtedness and obligations of the Maker (such
indebtedness of the Maker to which this instrument is subordinate and junior
being referred to as "Superior Debt"). The Superior Debt shall continue to be
Superior Debt and entitled to the benefits of these subordination provisions
irrespective of any amendment,



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modification or waiver of any term of the Superior Debt or extension or renewal
of the Superior Debt.

         3.03     Permitted Payments. Maker shall not make any regularly 
scheduled payment of accrued interest on any Subordinated Debt unless at the
time of such scheduled interest payment there exists no event of default under
the Superior Debt and so long as such payment would not thereby result in such
an event of default.

         3.04     Default on Superior Debt.

         (a)      In the event the Maker shall default in the payment of any
         principal or interest on any Superior Debt when the same becomes due
         and payable, whether at maturity or at a date fixed for prepayment or
         by declaration or otherwise, then, unless and until such default shall
         have been cured or waived or shall have ceased to exist, no direct or
         indirect payment (in cash, property or securities or by set-off or
         otherwise) shall be made or agreed to be made on account of the
         principal or interest on any Subordinated Debt, or as a sinking fund
         for the Subordinated Debt, or in respect of any redemption, retirement,
         purchase or other acquisition of any of the Subordinated Debt.

         (b)      Upon the happening of an event of default with respect to any
         Superior Debt, as defined in the instrument under which the same is
         outstanding, which occurs at the maturity of same or which permits a
         Bank to accelerate the maturity of the Superior Debt (other than under
         circumstances when the terms of SECTION 3.04(a) are applicable), then,
         unless and until such event of default shall have been cured or waived
         or shall have ceased to exist, no direct or indirect payment (in cash,
         property or securities or by set-off or otherwise) shall be made or
         agreed to be made on account of the principal of, or premium, if any,
         or interest on any Subordinated Debt, or as a sinking fund for the
         Subordinated Debt, or in respect of any redemption, retirement,
         purchase or other acquisition of any of the Subordinated Debt, during
         any period:

                  (i)      after written notice of such default shall have been 
                  given to the Maker by any Bank; or

                  (ii)     in which any judicial proceeding shall be pending in
                  respect of such default and a notice of acceleration of the
                  maturity of such Superior Debt shall have been transmitted to
                  the Maker in respect of such default.

         3.05     Certain Events of Bankruptcy.  In the event of:

         (a)      any insolvency, bankruptcy, receivership, liquidation,
         reorganization, readjustment, composition or other similar proceeding
         relating to the Maker or to its creditors, as such, or to it property,



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         (b)      any proceedings for the liquidation, dissolution or other
         winding-up of the Maker, voluntary or involuntary, whether or not
         involving insolvency or bankruptcy proceedings.

         (c)      any assignment by the Maker for the benefit of its creditors, 
         or

         (d)      any other marshaling of the assets of the Maker, all Superior 
         Debt (including any interest on same accruing at the legal rate after
         the commencement of any such proceedings and any additional interest
         that would have accrued on same but for the commencement of such
         proceedings) shall first be paid in full before any payment or
         distribution, whether in cash, securities or other property, shall be
         made to Payee on account of any Subordinated Debt. Any payment or
         distribution, whether in cash, securities or other property, which
         would otherwise (but for these subordination provisions) be payable or
         deliverable in respect of this Subordinated Debt shall be paid or
         deliverable directly to the Banks (including any interest thereon
         accruing at the legal rate after the commencement of any such
         proceedings and any additional interest that would have accrued on same
         but for the commencement of such proceedings) shall have been paid in
         full.

         3.06     No Payments. In the event that any Subordinated Debt shall be
declared due and payable as the result of the occurrences of any one or more
defaults in respect of same, under circumstances when the terms of SECTION 3.04
are not applicable, no payment shall be made in respect of any Subordinated Debt
unless and until all Superior Debt shall have been paid in full or such
declaration and its consequences shall have been rescinded and all such defaults
shall have been remedied or waived.

         3.07     Payments in Trust. If any payment or distribution, whether in
cash, securities or other property, shall be received by Payee in contravention
of any of the terms of this Note and before all the Superior Debt shall have
been paid in full, such payment or distribution shall be received in trust for
the benefit of, and shall be paid over or delivered and transferred to, the
Banks for application to the payment of all Superior Debt remaining unpaid to
the extent necessary to pay all such Superior Debt in full. In the event of the
failure of Payee to endorse or assign any such payment or distribution, the
Banks are hereby irrevocably authorized to endorse or assign the same.

         3.08     Certain Rights of Subordinated Debt. The Banks shall not be
prejudiced in the right to enforce subordination of Subordinated Debt by any act
or failure to act on the part of the Maker. The foregoing provisions as to
subordination are solely for the purpose of defining the relative rights of the
Banks, on the one hand, and the Payee, on the other hand. Nothing contained
herein shall impair, as between the Maker and the Payee, the obligation of the
Maker, which is unconditional and absolute, to pay to the Payee the principal
hereof and interest on this Note as and when the same shall become due and
payable in accordance with the terms of this Note, or prevent the Payee from
exercising all rights, powers and remedies otherwise permitted by applicable law
or under this Note upon a default or Event of Default under this Note, all


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subject to the rights of the Banks to receive cash, securities or other property
otherwise payable or deliverable to the Banks.

         3.09     Future Action. The Payee will take such action (including, 
without limitation, the delivery of this instrument to an agent for the Banks or
consent to the filing of a financing statement with respect thereto) as may, in
the opinion of counsel designated by any Bank, be necessary or appropriate to
assure the effectiveness of the subordination effected by these provisions.

4.       DEFAULTS AND REMEDIES.

         4.01     Events of Default. An "Event of Default" shall occur if:

                  (a)      the Maker defaults in the payment of interest on this
         Note when the same becomes due and payable and such Default continues
         for a period of 30 days;

                  (b)      the Maker defaults in the payment of principal on 
         this Note when the same becomes due and payable, at maturity or
         otherwise;

                  (c)      the Maker fails to comply with any of the other
         agreements contained in this Note, and the Default continues for the
         period and after the notice specified below; and

                  (d)      the Maker pursuant to or within the meaning of any
         Bankruptcy Law (as defined below):

                          (i)      commences a voluntary case;

                          (ii)     consents to the entry of an order against it 
         for relief in an involuntary case; or

                          (iii)    makes a general assignment for the benefit of
         its creditors; or

                   (e)     a court of competent jurisdiction enters an order or
         decree under any Bankruptcy Law that:

                          (i)      is for relief against the Maker in an 
         involuntary case;

                          (ii)     appoints a Custodian (as hereinafter defined)
         for all or substantially all of the assets of the Company; or

                   (iii)   orders a liquidation of the Company.


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         The term "Bankruptcy Law" means Title 11, U.S. Code or any similar
federal or state law. The term "Custodian" means any receiver, trustee,
assignee, liquidator, or similar official under any Bankruptcy Law.

         A default under clause (c) above shall not constitute an Event of
Default until Payee notifies the Maker of the Default and the Maker does not
cure the Default within 60 days of such notice. The notice must specify the
Event of Default, demand that it be remedied, and state that it is a notice of
Event of Default.

         4.02     Remedy. If an Event of Default occurs and is continuing, the 
sole remedy of the holder of this Note shall be as set forth in SECTION 2.02
hereof.

5.       MISCELLANEOUS

         The undersigned hereby waives presentment, demand for payment, notice
of dishonor, and any and all other notices or demands in connection with the
delivery, acceptance, performance, default or enforcement of this Note, and
hereby consents to any extensions of time, renewals, releases of any party to
this Note, waivers or modifications that may be granted or consented to by the
Payee in respect to the time of payment or any other provision of this Note.
THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
(EXCLUSIVE OF THE LAWS GOVERNING CONFLICTS OF LAWS) OF THE COMMONWEALTH OF
MASSACHUSETTS.

                                  DYNAGEN, INC.

                                  By:/s/ Dhananjay Wadekar
                                     ------------------------
                                  Name: Dhananjay Wadekar
                                  Title:   Executive Vice President

To acknowledge limited recourse in accordance with Sections 2 and 4 of this
Note:

SOVEREIGN PARTNERS


By:
   ----------------------------------
Name: Steven Hicks
Title: President and General Manager


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