Linear sequence fragment examples

Figure 2 Examples of linear sequence fragments and ring descriptor developed for the CAS ONLINE screen dictionary. An example structure is given at the top. The sequences start from the acyclic carbon on the left and go along the bottom of the ring to the acyclic oxygen on the right. Bonds marked r are explicitly ring. Note that only the bond sequence has completely specific bond types.

Fig. 3. Three-dimensional structures of three examples of superstructures formed by sequence repeats a linear rod (the spectrin a-chain dimer [PDB 2spc]), a superhelix of repeats (armadillo repeats of importin a-subunit [PDB lbk5]), and a closed /3-propeller (WD40 repeats from a fragment of the /3-subunit of the guanine nucleotide binding protein 1 [PDB lgg2 chain B]).

Isoamijiol (159 Scheme 52), a linear 5,7,6-ring-fused member of the dolastane group of diterpenes, is the principal secondary metabolite in the brown seaweed Dictyota linearis. In the course of the synthesis of (159), Pattenden also used a photocycloaddition-fragmentation sequence. Treatment of (157) with HF as mentioned above yields the hydroazulenone portion (158) of (159), which then was elaborated to isoamijiol. This is the first example of a C=C bond and an Si—-O bond being used as push-i)uU partners in a fragmentation. 

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