(b) If the recorded contract provides for payments made or to be made by the purchaser before conveyance of title, including payments made at the execution of the contract, or if the recorded memorandum states that the contract so provides, the lien of the purchaser arising from any such payments actually made is enforceable against any such person described in paragraph (a) to the extent of such payments, not exceeding the total amount specified in the recorded contract or memorandum, and is so enforceable without regard to any notice of the estate or interest of such person. 5. The recording of the executory contract or memorandum shall be effective for the purposes of subdivision four up to and including the thirtieth day after the day fixed by the contract for the conveyance of title. An agreement extending the time for the conveyance of title, acknowledged or proved, and certified, in the manner to entitle a conveyance to be recorded, may be recorded, and the recording shall be effective up to and including the thirtieth day after the day fixed by such agreement for the conveyance of title. 6. An executory contract or memorandum thereof shall not be deemed recorded as provided in this section if it is recorded more than one year previous to the date on which the vendor acquired title to the real property to which the contract relates. An executory contract recorded before the date when the vendor acquired title shall not be deemed recorded as provided in this section as against a person to whom the real property is conveyed or contracted to be sold or exchanged, by a conveyance or contract which is part of the transaction in which the vendor acquired title. 7. An option to purchase or lease real property shall be deemed an executory contract within the meaning of this section, except that the recording of the option agreement shall be effective only up to and including the thirtieth day after the last day fixed by the agreement for the exercise of the option. If the option is exercised in accordance with the terms of the option agreement, the optionee may extend the effectiveness of the recording of the option agreement to and including the thirtieth day after the day fixed pursuant to the option agreement for the conveyance of title or the execution and delivery of the lease, as the case may be, by recording, within thirty days after the last day fixed by the option agreement for the exercise of the option, a written declaration executed by the optionor and the optionee, or by the optionee alone, and acknowledged or proved and certified in the manner to entitle a conveyance to be recorded, stating that the said option has been duly exercised and setting forth the day fixed pursuant to the option agreement for the conveyance of title or the execution and delivery of the lease, as the case may be. In the event that such declaration is executed by the optionee alone, it shall be verified by the optionee and shall also set forth the time and manner in which such option was exercised and, if the last day for the conveyance of title or the execution and delivery of the lease is not specified in the option agreement, the extension of the effectiveness of the recording of the option agreement shall in no event exceed ninety days from the date of the recording of such declaration. 8. (a) After the recording of an executory contract or memorandum has ceased to be effective as provided in subdivision five, or the recording of an option to purchase or lease real property has ceased to be effective as provided in subdivision seven, such executory contract, memorandum or option shall be (1) void as against a subsequent purchaser in good faith and for a valuable consideration, who has no other notice of an estate or interest of the contract vendee or optionee in the premises to which such contract, memorandum or option refers, or of any claim thereof, and (2) ineffective to give notice to such subsequent purchaser of any estate or interest of the contract vendee or optionee in such premises, or of any claim thereof, or to create any duty of inquiry with respect thereto.

(b) For the purposes of this subdivision, "purchaser" includes a person who purchases or acquires by exchange or contracts to purchase or acquire by exchange the same premises or any portion thereof or estate or interest therein, or acquires by assignment the rent to accrue from tenancies or subtenancies thereof in existence at the time of the assignment.