The Mannich reaction between a phenol and a chiral oxazinone is used as a key step in a concise synthesis of a highly functionalized, orthogonally protected amino triol. The utility of such an approach is illustrated by a concise synthesis of a highly oxygenated tetrahydroisoquinoline, a key structural unit of ecteinascidin 743 (Et 743) and related natural products.
ecteinascidin 743 (Et 743) - Mannich reaction - Pomerantz-Fritsch cyclization - oxazinone - tetrahydroisoquinoline