Two of Soho’s historic cast-iron structures, including an 1867-built stunner, are going the way of high-end condos. At the behest of developer Michael Kirchmann of GDS Development, the two five-story buildings are being converted from mixed-use properties into one condo development that will take the name, and address, 25 Mercer. Project brokers Fredrik Eklund and John Gomes of Douglas Elliman just announced the roll-out the building’s teaser site, which promises “five exclusive residences, ranging from townhouse, to lofts, to penthouse” in the Soho Cast-Iron District. According to Eklund, the development will have one townhouse with an elevator and “multiple terraces,” three floor-through lofts, and one duplex penthouse with a pool