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Drüsenfarbstoffe aus Labiaten: Strukturen von 16 Diterpenen (Coleone und Royleanone) aus Coleus coerulescens GÜRKE
Author(s) -
Grob Konrad,
Rüedi Peter,
Eugster Conrad Hans
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610235
Subject(s) - coleus , chemistry , stereochemistry , pigment , biosynthesis , ring (chemistry) , nucleophile , solvent , medicinal chemistry , botany , organic chemistry , enzyme , biology , catalysis
Leaf‐gland pigments from labiatae: structures of 16 diterpenoids (coleons and royleanones) from Coleus coerulescens G ÜRKE The Abyssinian labiate Coleus coerulescens has been investigated for its leaf‐gland pigments. From the very complex mixture of abietanoic diterpenoids the following pure constituents were isolated and their structures established: (1) Diosphenols : coleon C ( 1a ), 16‐O‐acetyl‐coleon C ( 1b ), coleon W ( 1f ); (2) A/B ‐trans‐6, 7‐diketones: coleon D ( 2b ), 16‐O‐acetyl‐coleon D ( 2c ), coleon V ( 2a ); (3) Spiro ‐coleons: 7,12‐bis(O‐desacetyl)‐coleon N( 3a ), 12‐O‐desacetyl‐coleon N ( 3b ), coleon O ( 4 ), 6,12‐bis (O‐desacetyl)‐coleon R ( 5a ), 12‐O‐desacetyl‐coleon R ( 5b ), 3‐O‐desacetyl‐3‐O‐formyl‐coleon Y ( 5g ); (4) Royleanones : The abeo‐compounds 6a , 6b , and 7 .Main compounds are 3b , 5e and 5g . This is the first record of a co‐occurrence of diosphenols, 6,7‐dioxo‐coleons, spiro‐coleons and royleanones. Preliminary experiments show that solvolytic opening of the cyclopropane‐ring followed by tautomerisation, oxidation to hydroxy‐p‐benzoquinones or elimination to quinomethanes and subsequent nucleophilic attack of the solvent leads to compounds with a 2′‐substituted propyl group at C(13), thus supporting the biosynthesis of the unusual coleon E side chain.