title: Structure revision and syntheses of epohelmins A and B.
abstract: [structures: see text] Epohelmins A (24) and B (26) have been reassigned as pyrrolizidin-1-ols, rather than the proposed 9-oxa-4-azabicyclo[6.1.0]nonane structures 1 and 2, respectively. Syntheses of epohelmin A (24) (eight steps, 52% overall yield) and epohelmin B (26) (11 steps, 43% overall yield) have been achieved starting from N-Cbz-(S)-prolinal (9) and ortho ester ketone 17 using a stereoselective aldol reaction and a stereoselective reductive cyclization as the key steps.
authors.affiliation: Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110, USA. snider@brandeis.edu
authors.forename: Barry B
authors.initials: BB
authors.lastname: Snider
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Gao
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism; D003500:Cyclization; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; C494514:epohelmin A; C494515:epohelmin B