Nachweis von C (15)-epimeren Coleonen C und D in der Natur und ihre Bedeutung für den sterischen Verlauf der Bildung des Spirocyclopropanrings
✍ Scribed by Peter Rüedi; Jean Martin Schmid; Conrad Hans Eugster
- Publisher
- John Wiley and Sons
- Year
- 1982
- Tongue
- German
- Weight
- 412 KB
- Volume
- 65
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Natural Occurrence of C(15)‐Epimeric Coleons C and D and its Significance to the Stereochemistry of the Formation of a Spirocyclopropanring
In a previous paper some evidence was presented for a predominant occurrence of epimeric coleons ((15__S__)‐coleon C ((15 S)‐1a), and (15__S__)‐coleon D ((15__S__)‐2a)) in Plectranthus lanuginosus [1], The proposed structures have now been proven by careful comparison of their physical data with those of the already described C(15)‐epimers whose structures were deduced by X‐ray analysis of a derived cis‐diketone 3 [5], Examination of the epimeric purity of coleons possessing a 2‐hydroxy‐1‐methylethyl side‐chain (coleons C, D, H, I, I′ and derivatives) isolated from seven different species (Coleus, Plectranthus and Solenostemon) has shown that these coleons always occur as a mixture of C(15)‐epimers, although in most cases with one predominant epimer. The consequences for the stereochemistry of the postulated in vivo formation of the methyl‐substituted spirocyclopropane substructure is discussed.