The chartellines (1-3; Scheme 1) were isolated from the marine bryozoan Chartella papyracea in the 1980s by Christophersen and co-workers. [1] The core structure of the chartellines includes a b-lactam, an indolenine, and 2bromoimidazole. In addition, these natural products have a unique rigid, folded conformation resulting from p-p stacking between the indolenine and imidazole. To date, Baran et al. have reported the only a racemic total synthesis of chartelline C, [2] and several other groups have reported synthetic approaches to the chartellines. [3][4][5][6] Herein, we disclose a stereoselective construction of the core skeleton of chartelline C.Our retrosynthetic analysis is shown in Scheme 2. We envisioned that the enamide moiety in 3 would be constructed by elimination of a hydroxy group at the position b to the lactam nitrogen on the ten-membered ring. Formation of the b-lactam would be performed by a stereoselective alkylation at the 3-position of the indole, with the stereochemistry controlled by the conformation of the ten-membered ring in intermediate 4. The conformation would be affected by the secondary hydroxy group on the ten-membered ring. The tenmembered ring in 4 would be synthesized by an intramolecular Mitsunobu reaction of nosyl amide 5, [7] which could be derived from 6 by introduction of a nitrogen atom at the 3-position of the indole through a diazo coupling reaction, [8] Scheme 1. Structure of chartellines.Scheme 2. Retrosynthesis. Ns = nitrobenzenesulfonyl.Scheme 3. a) NIS, ClCH 2 CH 2 Cl, RT; Na 2 SO 3 , EtOH/H 2 O (3:1), reflux; b) SEMCl, iPr 2 NEt, TBAI, THF/ClCH 2 CH 2 Cl (1:1), reflux, 94 % (2 steps); c) tri-n-butyl(vinyl)tin, [Pd(PPh 3 ) 4 ], o-xylene, reflux, 97 %; d) OsO 4 , NMO, acetone/H 2 O (1:1), RT, 93 %; e) TBSOTf, iPr 2 NEt, CH 2 Cl 2 , 08C, 95 %; f) DIBAL, CH 2 Cl 2 , À78 8C; g) 13, K 2 CO 3 , MeOH, RT, 96 % (2 steps). DIBAL = diisobutylaluminum hydride, NIS = N-iodosuccinimide , NMO = N-methylmorpholine N-oxide, SEM = 2-(trimethylsilyl)ethoxymethyl, TBAI = tetra-n-butylammonium iodide, TBS = tertbutyldimethylsilyl, Tf = trifluoromethanesulfonyl.