The diazo route to diazonamide A. Studies on the indole bis-oxazole fragment

[structure: see text] Various approaches to the indole bis-oxazole fragment of the marine secondary metabolite diazonamide A are described, all of which feature dirhodium(II)-catalyzed reactions of diazocarbonyl compounds in key steps. Thus, 3-bromophenylacetaldehyde is converted into an alpha-diazo-beta-ketoester, dirhodium(II)-catalyzed reaction of which with N-Boc-valinamide resulted in N-H insertion of the intermediate rhodium carbene to give a ketoamide that readily underwent cyclodehydration to give (S)-2-(1-tert-butoxycarbonylamino)-2-methylpropyl]-5-(3-bromobenzyl)oxazole-4-carboxamide, after ammonolysis of the initially formed ester. This aryl bromide was then coupled to a 3-formyl-indole-4-boronate under Pd catalysis to give the expected biaryl. Subsequent conversion of the aldehyde group into a second alpha-diazo-beta-ketoester gave a substrate for an intramolecular carbene N-H insertion, although attempts to effect this cyclization were unsuccessful. A second approach to an indole bis-oxazole involved an intermolecular rhodium carbene N-H insertion, followed by oxazole formation to give (S)-2-[1-tert-(butoxycarbonylamino)-2-methylpropyl]-5-methyloxazole-4-carboxamide. A further N-H insertion of this carboxmide with the rhodium carbene derived from ethyl 2-diazo-3-[1-(2-nitrobenzenesulfonyl)indol-3-yl]-3-oxopropanoate gave a ketoamide, cyclodehydration of which gave the desired indole bis-oxazole. Finally, the boronate formed from 4-bromotryptamine was coupled to another diazocarbonyl-derived oxazole to give the corresponding biaryl, deprotection and cyclization of which produced a macrocyclic indole-oxazole derivative. Subsequent oxidation and cyclodehydration incorporated the second oxazole and gave the macrocyclic indole bis-oxazole.     

Studies on the mechanism of the Cadogan-Sundberg indole synthesis

The Cadogan-Sundberg indole synthesis produces two major products from the treatment of 2-nitrostilbenes with triethyl phosphite, which are the 2-arylindoles and the corresponding 2-aryl-N-ethoxyindoles. We were interested in determining the origin of the oxygen atom in the 2-aryl-N-ethoxyindoles. In this study, we verify that this oxygen atom originates from the nitro group and not from the triethyl phosphite.     

Studies on the synthesis of pentacyclic strychnos indole alkaloids. photocyclization of n-chloroacetyl-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole derivatives

Photocyclization of 2-chloroacetyl-1,2,3,4,5,6-hexahydro-1, 5-methanoazocino[4,3-b]indole ($\text{5}$) takes place at the indole 4-position to give a 1 ,2 ,3 ,4 , 5 ,6-hexahydro-2 ,11-ethano-1 ,5-methanoazocino [4 , 3-6] indole system. Consequently, the method appears to be unsuitable for constructing the pyrrolidine ring of pentacyclic Strychnos indole alkaloids.     

Studies on the biological activity of gem-difluorinated 3,3-spirocyclic indole derivatives

The biological activities of a series of 3,3-spirocyclic indole derivatives containing CF₂, phosphine oxide,indole, and cyano functional groups were evaluated, and these derivatives were found to exhibit antiTMV, fungicidal, and insecticidal activities.     

Studies on isocyanides and related compounds. Synthesis of furan derivatives and their transformation into indole derivatives

The intramolecular Knoevenagel condensation of N‐cyclohexyl 3‐aryl‐2‐(2‐nitrophenyl)acetoxy‐3‐oxopropionamides 4 obtained from 2‐nitrophenylacetic acid (1), arylglyoxals 2 and cyclohexyl isocyanide (3) afforded N‐cyclohexyl 3‐aryl‐2,5‐dihydro‐2‐(2‐nitrophenyl)‐5‐oxofuran‐2‐carboxamides 6 which underwent reductive cleavage to N‐cyclohexyl (Z)‐3‐aryl‐2‐hydroxy‐3‐(2,3‐dihydro‐2‐oxoindol‐3‐ylidene)propionamides 8 probably via the labile intermediates 7.     

Deformyl Corymine 类型的四个吲哚生物碱^1^3CNMR的研究

本文报道了四个deformyl corymine 的吲哚生物碱的^1^3C谱的归属, 对一些取代基效应进行了讨论; 并应用了C-HCOSY及选择去偶技术, 指认^1^3C信号。     

Studies on the Fischer indole synthesis: Behaviour of cyclic hydrazones of tetrahydropyridazine and pyrazoline series in polyphosphoric acid.

Heating 1,3-diphenyl-1,4,5,6-tetrahydropyridazine in PPA affords mainly 4-benzoyl-1,2,3,4-tetrahydroquinoline and 2-anilinopropiophenone. In analogous conditions 1,5-diphenyl-3-methyl-2-pyrazoline gives 2-styrylindole, benzidine and benzylideneacetone.     

Total synthesis of indole and dihydroindole alkaloids. IX. Studies on the synthesis of bisindole alkaloids in the vinblastine-vincristine series. The biogenetic approach.

A detailed study of the reaction of catharanthine N-oxide and vindoline has been carried out employing various conditions. Under optimum conditions, which involve low temperatures and trifluoroacetic anhydride as reagent, 3′, 4′-dehydrovinblastine (XIII, R = COOCH₃), in reasonable yields is essentially the exclusive product. However two additional products, 18′ (epi)- 3′, 4′-dehydrovinblastine (XIV, R = COOCH₃) and 1′-hydroxy- 3′, 4′-dehydrovinblastine (XVI, R = COOCH₃) are also often isolated. The reaction, which follows the course of a Polonovski-type fragmentation process, has been extended to the N-oxide derivatives of dihydrocatharanthine and decarbomethoxycatharanthine to provide again a series of bisindole alkaloid derivatives, also vinblastines. A mechanistic rationale is provided to explain the various results obtained.