Aflatoxins enantioselective total syntheses

The enantioselective total synthesis of (-l-)-aflatoxin Bi has been achieved by O-allylation with y-acyloxybutenolide and reductive Heck reaction [76]. The couma-rin derivative 199 was 0-allylated with y-O-Boc-butenolide 200, which is an... 

In 2003, Trost and Toste presented the first enantioselective total synthesis of aflatoxins Bj (1) and 82a (46) 40, 41). In Scheme 2.6, their synthesis is shown. The starting material for this sequence is catechol 40. A Pechmann condensation with diethyl p-oxoadipate and iodination with iodine chloride gave the lactone 41. 

Scheme 2.7 Enantioselective total synthesis of aflatoxin B2 (2). Reagents and conditions a) 51, CH2CI2/CH3CN, -78°C to It, 7 h, 65%, 99% ee b) hexamethylenetetramine, HOAc, 110°C, 48 h, 40% c) DMAP (cat.), pyridine, TfiO, CH2CI2, -20°C to 0°C, 80% d) MeMgBr, THF, -20°C, 2 h e) DMP, CH2CI2, 0°C to rt, 85% over two steps f) TFAA, urea H20, CH2CI2, rt, 63% g) Raney-Ni, H2, MeOH, rt, 3 h, 60% h) NaHCOs, ZnCOs, ethyl 2-bromo-5-oxocyclopent-l-enecarboxylate, CH2CI2, rt, 20 h, 36%...

Trost BM, Toste FD (2003) Palladium Catalyzed Kinetic and Dynamic Kinetic Asymmetric Transformations of y-Acyloxybutenolides. Enantioselective Total Synthesis of (-) Aflatoxin Bl and B2a. J Am Chem Soc 125 3090... 

Zhou G, Corey EJ (2005) Short, Enantioselective Total Synthesis of Aflatoxin B2 Using an Asymmetric [3+2]-Cycloaddition Step. J Am Chem Soc 127 11958... 

In 2003, Trost s group developed the Pd-catalysed DKR of y-acyloxy-butenolides and apphed this methodology to the first enantioselective total synthesis of ( )-aflatoxins B2a and Bi, as shown in Scheme 2.53. This methodology was also apphed to the total synthesis of (-I- )-brefeldin... 

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