(charitable deduction for donation of "qualified conservation contribution" of $6,570,000 disallowed for LLC that donated lot and townhouse constructed in 1894 in New York City to qualified organization for failure to meet perpetuity requirement of I.R.C. Sec. 170(h)(5)(A); lender agreement with respect to subject property clearly stated that lender retained a "prior claim" to all condemnation and insurance proceeds" in preference to donee until mortgage satisfied and discharged - thus, until mortgage repaid, possibility existed that lender could deprive donee of value that was required to be dedicated to conservation purpose - non-compliance with perpetuity requirements of Treas. Reg. Sec. 1.170A-14(g)(6)(ii)).