<abstract abstract-type="toc"> <title> <x xml:space="preserve">Abstract</x> </title> <p> <graphic position="anchor" id="ga" xlink:href="ark:/27927/pgj26b8j8fb" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" />Natural and modified substrates coupled with LC-MS/MS analysis of products revealed the stereospecificity and stereoselectivity of a polyketide didomain.</p> </abstract>