83088-43-1Relevant academic research and scientific papers
Total Synthesis of the Spirans of Cannabis: Cannabispiradienone, Cannabispirenone-A and -B, Cannabispirone, α- and β-Cannabispiranols and the Dihydrophenanthrene Cannithrene-1
Crombie, Leslie,Tuchinda, Patoomratana,Powell, Michael J.
, p. 1477 - 1484 (2007/10/02)
O-Methylcannabispirenone has been synthesised (57percent overall from 3,5-dimethoxycinnamic acid) via 5,7-dimethoxyindanone, p-tolylsulphonylmethyl isocyanide conversion into the 1-nitrile, alkylation with 1-iodo-3,3-ethylenedioxybutane, deacetalisation, and spirocyclisation. 5,7-Dimethoxyindanone is 7-deprotected by boron trichloride with high selectivity, and re-protected as the methoxyethoxymethyl ether: following the above route, finally deprotecting by boron trichloride, gives cannabispirenone-A (2) in 21percent overall yield.O-Methylcannabispirenone can be demethylated to give (2) by lithium 1,1-dimethylethanethiolate: demethylation with boron tribromide gives cannabispirenone-B (3).Hydrogenation of synthetic cannabispirenone-A gives cannabispirone (4), reduced by borohydride to the epimeric α-(6) and β-(5) cannabispiranols, separated by h.p.l.c.Dehydrogenation of O-methylcannabispirenone with dichlorodicyanobenzoquinone, followed by lithium 1,1-dimethylethanethiolate demethylation, gives cannabispiradienone (1).Under acidic conditions, the latter undergoes dienone-phenol rearrangement to give cannithrene-1 (8), thus completing the total synthesis of the spiro-cannabinoid group of natural products discussed in the preceding paper.The unsubstituted cannabispirenone parent has also been synthesised.
