Myochrysine contains the thiomalate ligand and is an anti-arthritic drug and has a polymeric structure in the solid state:

The backbone of the polymer is a helical chain of alternating Au and S atoms, and pairs of chains form double helices (Fig. 22.38). 

(a) Is the double helix in Fig. 22.38 chiral? Rationalize your answer.

(b) Why is the thiolate ligand chiral? 

(c) Starting with a racemic mixture of (R)- and (S)-thiomalate, two structurally distinct double helices are observed in the unit cell of Myochrysine. Explain why this is.

(d) The shortest Au · · · Au contacts between the two chains in the double helix in Fig. 22.38 are 323 pm. Comment on the importance of such interactions in Au(I) chemistry. 

(e) Myochrysine is a prodrug. Explain what this means, and outline a possible means for uptake of Au(I) by the body.

Figure 22.38.

Transcribed Image Text:

Au CO₂ Na+ ta) H CO₂ Na* n