A chemical study of burley tobacco flavour (Nicotiana tabacum L.) VI. Identification and synthesis of four irregular terpenoids related to solanone, including a 'prenylsolanone'.

Four novel constituents of Burley tobacco condensate have been identified as (E)-5-isopropyl-7-(2-methyl-tetrahydrofur-2-yl)-hept-6-en-2-one ( G ), (E)-5-isopropyl-7-(2-methyl-tetrahydrofur-2-yl)-hept-6-en-2-ol ( H ), (E)-4-methyl-7-isopropyl-10-oxo-undec-5-en-4-olide ( I ), and (E, E)-6,12-dimethyl-9-isopropyltrideca-5,10,12-trien-2-one ( J ) or ‘prenylsolanone’. Compounds G , H , and I were synthesized from norsolanadione ( 1 ), compound J from solanone ( A ). These substances belong to a growing family of tobacco metabolites structurally related to solanone ( A ). Their possible formation from cembrene-type precursors is briefly outlined.     

Simple construction of bicyclo[4.3.0]nonane,bicyclo[3.3.0]octane,and related benzo derivatives by palladium-catalyzed cycloalkenylation

[reaction: see text] Bicyclo[4.3.0]nonanes (hydrindanes) and bicyclo[3.3.0]octanes (octahydropentalenes) are easily synthesized by palladium-catalyzed cycloalkenylations. Additionally, benzo-fused bicyclo[3.3.0]octanes are prepared for the first time through intramolecular coupling between silyl enol ethers and aromatic rings in the presence of catalytic palladium acetate.     

Oxidative and hydrolytic cleavage of cyclopropane and spirocyclobutane derivatives of 6,8-dioxabicyclo[3.2.1]octane,the products of transformation of levoglucosenone

A new method for the synthesis of (1R,4S,5S)-4-hydroxymethyl-3-oxabicyclo[3.1.0]hexan2-one, the cyclopropane analog of (S)-5-hydroxypent-2-en-4-olide, has been suggested based on oxidation of (1S,2S,4R,6R)-7,9-dioxatricyclo[4.2.1.0^2,4]nonan-5-one. Oxidation of cyclobutanones, spirojoined with the fragments of 6,8-dioxabicyclo[3.2.1]oct-2-ene, 6,8-dioxabicyclo[3.2.1]octane (at position 4), or 7,9-dioxatricyclo[4.2.1.0^2,4]nonane (at position 5), upon the action of m-chloroperoxybenzoic acid or the KMnO₄-H₂SO₄-H₂O system leads to the corresponding spirojoined butanolides in 73–85% yields. The same cyclobutanones easily undergo the four-membered ring opening upon the action of dilute H₂SO₄ at 50–90 °C to form 6,8-dioxabicyclo[3.2.1]octane-4- or 7,9-dioxatricyclo[4.2.1.0^2,4]nonane-5-propionic acid.     

A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.). II. Medium-Volatile,free Acidic Constituents (b.p. ∼84–114°/0.001 Torr)

The acidic part of a fraction b.p. 84–114°/0.001 Torr from Burley Tobacco condensate was investigated. Among the 22 compounds identified, 9 appeared to be new tobacco flavour components. This result increased to 208, the total number of Burley tobacco constituents so far isolated and identified in this laboratory.     

A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.). III. Structure Determination and Synthesis of 5-(4-Methyl-2-furyl)-6-methylheptan-2-one (“Solanofuran”) and of 3,4,7-Trimethyl-1,6- dioxa-spiro[4.5]dec-3-en-2-one (“Spiroxabovolide”), Two New Flavour Components of Burley Tobacco

Two novel constituents of Burley tobacco condensate were shown to be 5-(4-methyl-2-furyl)-6-methylheptan-2-one (solanofuran, 4 ) and 3,4,7-trimethyl-1,6-dioxa-spiro[4.5]-dec-3-en-2-one (spiroxabovolide, 6 ). These structures were deduced from spectral data and confirmed by synthesis. Solanofuran ( 4 ) was prepared via the dye-sensitized photo-oxygenation of solanone ( 1 ). This type of reaction involving the uncommon ‘diene-addition’ of ¹O₂ to a conjugated acyclic diene system was thus applied for the first time to the synthesis of a terpenoid furan, a route that might have some biogenetic significance. Both solanofuran ( 4 ) and spiroxabovolide ( 6 ) display interesting organoleptic properties. Identification of these compounds increases to 210 the total number of Burley tobacco flavour constituents so far characterized in this laboratory.     

A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacumL.) V. Identification and Synthesis of the Novel Terpenoid Alkaloids 1, 3, 6, 6-Tetramethyl-5, 6, 7, 8-tetrahydro-isoquinolin-8-one and 3, 6, 6-Trimethyl-5,6-dihydro-7H-2-pyrindin-7-one

GLC. allowed the isolation of 1, 3, 6, 6-tetramethyl-5, 6, 7, 8-tetrahydro-isoquinolin-8-one (A) and 3,6,6-trimethyl-5,6-dihydro-7H-2-pyrindin-7-one (D) from Burley tobacco condensate (about 0.1% each). The structures and syntheses of these novel terpenoid alkaloids are described, and a possible way for their formation in tobacco is suggested.