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. Author manuscript; available in PMC: 2010 Jan 1.
Published in final edited form as: Angew Chem Int Ed Engl. 2009;48(31):5648–5652. doi: 10.1002/anie.200902029

Scheme 3.

Scheme 3

Synthesis of vannusal B structure 3. Reagents and conditions: (a) SmI2 (0.1 M in THF, 10 equiv), HMPA (30 equiv), THF, −20→25 °C, 20 min, 67 %; (b) Ac2O (20 equiv), Et3N (20 equiv), 4-DMAP (0.2 equiv), CH2Cl2, 25 °C, 30 min, 100 %; (c) SEMCl (10 equiv), iPr2NEt (30 equiv), CH2Cl2, 50 °C, 18 h; (d) DIBAL-H (5.0 equiv), CH2Cl2, −78 °C, 30 min, 83 % for two steps; (e) NaH (10 equiv), CS2 (3.0 equiv), THF, 0→25 °C, 30 min; then CH3I (6.0 equiv), 0→25 °C, 1 h, 79 %; then 185 °C (μ–waves), 1,2-dichlorobenzene, 15 min, 88 %; (f) KHMDS (4.0 equiv), SEMCl (4.0 equiv), Et3N (8.0 equiv), THF, −50→25 °C, 20 min, 78 %; (g) ThexBH2 (5.0 equiv), THF, −10→25 °C, 30 min; then BH3•THF (15 equiv), 25 °C, 1 h; then 30 % H2O2/3 N NaOH (1:1 dr), 25→45 °C, 30 min; 71 % (1:1.3 mix); (h) oNO2C6H4SeCN (3.0 equiv), nBu3P (9.0 equiv), py (12.0 equiv), THF, 25 °C, 10 min; then 30 % H2O2, 25→45 °C, 30 min, 86 %; (i) KHMDS (6.0 equiv), TESCl (4.0 equiv), Et3N (8.0 equiv), THF, −50→25 °C, 20 min, 93 %; (j) LiDBB (excess), THF, −78→−50 °C, 30 min, 85 %; (k) PhI(OAc)2 (4.0 equiv), TEMPO (2.0 equiv), CH2Cl2, 25 °C, 15 h, 88 %; (l) Ac2O (30 equiv), Et3N (60 equiv), 4–DMAP (2.0 equiv), CH2Cl2, 25 °C, 24 h, 100 %; (m) aq. HF:THF (1:3), 25 °C, 6 h, 90 %. KHMDS = potassium hexamethyldisilyazide, TEMPO = 2,2,6,6-teramethyl-1-piperidinyloxy free radical, Thexyl = thexylborane, LiDBB = Lithium di-tert-butylbiphenyl.