Dibenzazecines

Dibenzazecines are probably biogenetically derived from a phenethyliso-quinoline such as 112 via the homoproerythrinadienone 113 (Scheme 33). The resulting dibenzazecine can either give dysazecine 114 or be further oxidized to a homoerythrina derivative such as 115. This biogenetic pathway parallels that of the Erythrina alkaloids (see Scheme 32). 

Teitel et al. prepared tetracyclic benzazepineisoindole, i.e., Schopf s base VI (104a), from /3-hydrastine (100, 675). This base is a convenient intermediate for further chemical transformation into the protopine skeleton Hofmann degradation of the base VI yields the compounds 105 (isoindoline structure) and 106. The 10-membered trans- (108b) and cis-dibenzazecine (106) were converted via 107 into a -allocryptopine (101b) in poor yield (Scheme 38). 

Diazo-3-oxo-l -phenyl-1 -butene, 5 97 Dibenzazecine, 481 Dibenzazonine alkaloids, 660 Dibenzo-15-crown-5, 174 Dibenzo-18-crown-6, 159-160, 174 Dibenzoylacetylene, 150... 

Fig. 3. Phenethylisoquinolines 47 and 48 isolated from plants, which produce homoerythrinane and dibenzazecine alkaloids 49, 50, and 51...

The first syntheses of the homoerythrinane framework are following the assumed hiosynthetic route. Thus, the N-protected 1-phenethyliso-quinoline 196 (Scheme 35) can be cyclized by a phenol oxidative procedure providing the tetracyclic naphthalenoisoquinoline 197, a homologue of neoproaporphine (35) in 35-45% yield (105). This has been transformed to the dibenzazecine intermediate 198 by ring reopening. Finally, the N-deprotected free amine base can be oxidized giving homoerysodienone (199) (106, 107). A diphenoquinone type intermediate 38 (Scheme 1 n = 2) is not available from the N-acylated base 198. 

Aladesanmi AI, Kelley CJ, Leary ID (1983) The Constituents of Dysoxylum lenticellare, I. Phenylethylisoquinoline, Homoerythrina, and Dibenzazecine Alkaloids. J Nat Prod 46 127... 

Tanaka H, Tamura Y, ShibataM,lto K( 1986) A Novel Conversion of Dibenzazecines into Homoerythrina Compounds Synthesis of cw-16,17-Dimethoxyhomoerythrinan-3-one. Chem Pharm Bull 34 24... 

The biphenyl bond of dibenzazonine and dibenzazecine systems has been formed by the benzyne reaction—induced with dimsyl sodium—of 2 -halo-benzyl- and 2 -halophenethyltetrahydroisoquinolines, respectively. (See Sec. 8.1.1 for related conversions.) Reductive deoxygenation of product 3 to the sulfide stage followed by Raney nickel desulfurization afforded dibenzazonine 4 and dibenzazecine 5 in unspecified yields (see Scheme 18.2). ... 

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