Synthetic approaches to spiroaminals

The 1-oxa-7-azaspiro[5.5]undecane, 1-oxa-6-azaspiro[4.5]decane, 1-oxa-7-azaspiro[5.4]decane and 1-oxa-6-azaspiro[4.4]nonane ring systems are found as the cores of natural or synthetic products that possess significant biological activities. Because of their potential applications, together with the novelty of their skeletons, these compounds represent challenging targets for chemical synthesis. In this review we summarize the different strategies developed for the synthesis of these spiroaminals. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008.