Total Synthesis Highlights
Total Synthesis Highlights
Total Synthesis Highlights
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The convergent coupling of 1 with 2 was carried out under Suzuki conditions. Reduction of the<br />
iodide of 2 to the corresponding alkyl lithium followed by exchange with B-OMe-9-BBN gave<br />
gave an intermediate organoborane, that smoothly coupled with 1 under Pd catalysis to give 18.<br />
Deprotection and carbamate formation then led to (+)-discodermolide (3).<br />
This synthesis clearly illustrates the power of 5 as an enantiomerically-defined secondary<br />
organometallic reagent, and the synthetic versatility of the product alkenyl carbamates. The ready<br />
availability of the three enantiomerically-pure four-carbon fragments 4, 8, and 14 was also a key<br />
consideration in the design of this synthesis.<br />
37. The Maier <strong>Synthesis</strong> of Cruentaren A<br />
Cruentaren A (3), isolated from the myxobacterium Byssovorax cruenta, is an inhibitor of<br />
mitochondrial F-ATPase. The synthesis of 3 (Org. Lett. 2007, 9, 655,; Angew. Chem. Int. Ed. 2007,<br />
46, 5209.) by Martin E. Maier of the Universität Tübingen illustrates the power of alkyne<br />
metathesis as a tool for the synthesis of complex natural products. Very recently, Alois Fürstner of<br />
the Max-Planck-Institut, Mülheim, reported (Angew. Chem. Int. Ed. 2007, 46, 9275.) an<br />
alternative synthesis, also based on alkyne metathesis, of cruentaren A (3).<br />
The alcohol portion of 1 was prepared by Marshall homologation of 4 with 5, leading to 6.<br />
Homologation of the derived epoxide 7 then gave 8. Note that the homologation of 7 to 8 required<br />
three steps. This might have been accomplished more directly with the Li salt of 1-propyne, easily<br />
prepared from commercial 1- or 2-bromopropene.