Li and Nicolaou

Fig. 6.7 Simplified scheme of the copying process in DNA replication via triple helices, as described by Li and Nicolaou (Ferris, 1994)...

Figure 7.9 The triple-helix self-replication scheme by Li and Nicolaou, 1994 (adapted) S1 and S2 are the two strands, and FI and F2 the two fragments. Purine strands are black pyrimidine strands are white. For the precise meaning of the symbols in the figure, see the original paper.

A higher degree of complexity is offered by the elegant work by Nicolaou and coworkers (Li and Nicolau, 1994) (see Figure 7.9). In this case, the self-replication of DNA is based on a triple helix. 

It is also of interest to note that Wai-Kee Li, who performed the calculation on the diradical p-benzyne, as well as Wei-Min Dai, who coauthored the informative review article with Nicolaou, are now my colleagues at the Chinese University of Hong Kong and the Hong Kong University of Science and Technology, respectively. 

The majority of reactions required to form these types of heterocycles involve the condensation of a 1,2-diamine and a 1,2-dicarbonyl compound, as shown in Equation (46) <2000H(52)423>. Other examples include the reaction of enaminones with carboxamides (Equations 47 and 48) <199681012, 2000T8489> and the cyclocondensation of a-ketoesters (Equation 49) <2001FA933>. Nicolaou and Li have prepared 99 and 100 by reaction of the diol 101 with a-bromoisobutyraldehyde (Equation 50) <2001AGE4264>. 

For a recent and elegant use of the Claisen rearrangement for the construction of complex ortho-quinol intermediates in the total synthesis of morellin natural products, see K. C. Nicolaou, J. Li,... 

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