Stereochemistry of pyrrolizidine alkaloid biosynthesis: incorporation of chiral[1-2H]putrescines into retrorsine
Abstract
2 H N.m.r. spectroscopy has been used to establish the labeling patterns in retrorsine (1) derived biosynthetically from (R)-[1-2H]-putrescine; in the former case retrorsine (11) is equally labelled with 2H at the 3β, 5α, 8α and 9-pro-S positions, while with the latter precursor only the 3α and the 5β positions in retrorsine (15) are labelled with 2H.