In Natural Product Synthesis

Cleavage of silyloxiranes (e.g. 55) by methanol, leading to aldehydes or ketones (e.g. 56 Scheme 48), has found use in natural products synthesis (8UA1831, 80JA5004). 

Oxirane opening by functionalized ethenylaluminum (81JA1851) and ethenylcopper (79JCS(Pl)2954) reagents has found applications in natural products synthesis. 

The condensation reaction of a CH-acidic compound—e.g. a ketone 3—with formaldehyde 1 and ammonia 2 is called the Mannich reaction, the reaction products 4 are called Mannich bases. The latter are versatile building blocks in organic synthesis, and of particular importance in natural products synthesis. 

The Neber rearrangement has for example found application in natural product synthesis. 

The intramolecular Sakurai reaction allows for the synthesis of functionalized bicyclic systems. By proper choice of the reaction conditions, especially of the Lewis acid or fluoride reagent used, high stereoselectivity can be achieved, which is an important aspect for its applicability in natural products synthesis. 

The Sharpless epoxidation is one of the most important of the newer organic reactions. Although limited to allylic alcohols, it has found wide application in natural product synthesis. 

Nicolaou, K.C. Petasis, N. A. Selenium in Natural Products Synthesis, CIS Philadelphia, 1984. 

Mori et al. have demonstrated the most dramatic uses of lithiated epoxides in natural product synthesis [62]. By employing the chemistry developed by Jackson, and subsequently performing a Lewis acid-catalyzed (BF3 OEt2) cyclisation, tetra-hydrofuran, tetrahydropyran, and oxepane rings are readily accessed this strategy is demonstrated by the synthesis of the marine epoxy lipid 173 (Scheme 5.40) [63]. 

Diene, Enyne, and Diyne Metathesis in Natural Product Synthesis... 

A highlight in the application of RCM methodology in natural product synthesis is Hirama s total synthesis of ciguatoxin CTX3C (183) [90], including the more recent improved protective group strategy, as depicted in Scheme 34 [90b]. The structure of 183 spans more than 3 nm and is characterized by 12 six- to nine-membered trans-fused cyclic ethers and a spiroannulated terminal tetra-... 

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