Synthesis of the carbazole alkaloids carbazomycin A and B and hyellazole

Total Synthesis of Marine Alkaloid Hyellazole and its Derivatives

“…[2] In 1979, hyellazole and 6-chlorohyellazole ( Figure 1) were the first carbazole alkaloids to be isolated from the blue-green alga Hyella caespitosa, a marine source, by Moore. Since the isolation of these alkaloids, more than fifteen different methods for their total synthesis [8][9][10][11][12][13][14][15][16][17][18] have appeared to date. This interesting structural features of these alkaloids enticed several research groups to devise different route for their total synthesis.…”

Synthesis of the staurosporine aglycone

“…3-Acetylindol-2-ylacetic Acid (70).-Potassium hydroxide solution (2 M; 11.8 ml) w a s a d de d to a solution of ethyl 3-acetylindol-2-ylacetate (69) (580 mg, 2.37 mmol) in tetrahydrofuran : methanol (9:1) (30 ml) and stirred at room temperature for 2 h. Water (100 ml) w a s added and the aqueous mixture extracted with ether (2 x 25 mi). T h e aqueous phase was acidified (pH 1.5) with dilute hydrochloric acid and extracted with ethyl acetate (4 x 30 ml).…”

“…Furthermore, the broad singlet corresponding to the enol proton in (61) Similarly, ethyl indol-2-ylacetate could be acetylated with acetyl chloride in the presence of tin (IV) chloride to give (69) in 93% yield (Scheme 2.17). This was also hydrolysed to the acid (70) and cyclodehydrated as shown below to give 1-methylpyrano [4,[3][4][5][6]indol-3-one (71).…”

“…T h e aqueous phase was acidified (pH 1.5) with dilute hydrochloric acid and extracted with ethyl acetate (4 x 30 ml). These extracts were wa sh ed with brine, dried ( M g S 0 4), and concentrated in vacuo to yield the title compound (70) "\-Methylpyrano [4,3-b]indoi-3-one (71).^Acetic anhydride (1 ml) w a s added to a solution of 3-acetylindol-2-ylacetic acid (70) [4,3-b]indole-5-carboxylate (72).-To a cooled suspension (0 °C) of sodium hydride (12.9 mg, 0.32 mmol) in dimethylformamide (6 ml), w a s added dropwise a solution of pyrano [4,3-b]indol-3-one (68) (54 mg, 0.29 mmol) in dimethylformamide (10 ml).…”

Total Synthesis of Carbazomycins A and B

“…10,11) Therefore, carbazomycins have been receiving considerable attention, and there have been several reports on their total synthesis. [12][13][14][15][16][17][18][19][20][21][22][23] In the synthesis of these compounds, the methods used to construct the fully substituted benzene ring in their structure have been the main subject of synthetic strategies, because it is generally difficult to construct a fully substituted benzene ring from benzene derivatives by aromatic substitution and/or cross-coupling strategies due to a shortage of reliable methods for installing a functional group at the desired position.…”