Photooxidative dehydrogenation of Δ8-drimen-and Δ8-11-homodrimen-7-ones into α,α ′-dienones

Synthesis of Novel Tetranorlabdane Derivatives with Unprecedented Carbon Skeleton

“…4 So far, several syntheses of tetranorlabdanes have been performed based on ketoester 6. 5,9,12 This paper reports the continuation of our investigations 14,15 into the chemistry of (-)-sclareol (1) and describes new regio-and stereoselective syntheses of polyfunctional tetranorlabdanes (homodrimanes) starting from methyl 7oxo-13,14,15,16-tetranorlabd-8-en-12-oate (6).…”

“…Reduction of compound 6 with NaBH 4 in the presence of CeCl 3 •7H 2 O afforded exclusively methyl 7α-hydroxy-13,14,15,16-tetranorlabd-8-en-12-oate (12) and its dehydration under mild conditions followed by 1,4-elimination led to methyl 13,14,15,16-tetranorlabd-6,8(9)-dien-12-oate (13). Sensitized photooxygenation 20 of diene 13 in CH 2 Cl 2 in the presence of meso-tetraphenylporphyrin (TPP) gave a mixture of methyl 6α,9α-peroxy-13,14,15,16-tetranorlabd-7(8)-en-12-oate (14), as a result of 1,4-cycloaddition, 21 and dioxine 15 from [2+2] singlet oxygen addition, 21 together with the known methyl 7-oxo-13,14,15,16-tetranorlabd-5,8(9)-dien-12-oate (16), 4,9 as a result of photooxidative dehydrogenation (Scheme 1).…”

“…In view of this, based on (-)-sclareol (1) and its derivative (+)-sclareolide (2), syntheses of important drimane sesquiterpenoids and some tetranorlabdanes have been performed via methyl bicyclohomofarnesoates 3-5 and methyl 7-oxo-13,14,15,16-tetranorlabd-8-en-12-oate (6, Figure 1). [3][4][5][6][7][8][9][10][11][12][13][14][15] Syntheses of tetranorlabdanes are generally shorter and easier than those of the related drimanes. Some of them have been applied on an industrial scale because the resulting tetranorlabdanes are used in perfumery, cosmetics, and tobacco products.…”