A Revised Preparation of Clemo's Tetrahydrobenzo-Quinolizinone

Synthesis of an Anti-Inflammatory 10,10a-Dihydro-lH,5H-imidazo[l,5-b]isoquinoline-l,3(2H)-dione

“…The target compound was readily prepared in a two-step sequence originating with the d,l-acid IV (6). Acid-catalyzed treatment of IV with potassium cyanate gave the unsubstituted 111, and treatment of 111 with N-(2-chloroethyl)piperidine (V) afforded d,l-11.…”

“…10,lOa-Dihydro-1 H,BH-imidazo[ 1,5-b]isoquinoline-l,3(2H)-dione (111)-To a suspension of 53.1 g (0.30 mole) of d,l-IV (6) in 1000 ml of acetic acid was added quickly a solution of 48.6 g (0.60 mole) of potassium cyanate in 150 ml of water. The mixture was stirred and heated on a steam bath at 90-95' for 90 min, and all solids were dissolved.…”

Synthesis of methylated phenylalanines via hydrogenolysis of corresponding 1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acids

“…is an interesting conformationally restricted analog of phenylalanine and a useful synthon for preparation of analogs of biologically active peptides (1-3), enzyme inhibitors (4, 5) etc. The only suitable synthesis of Tic described so far is Pictet-Spengler cyclization of phenylalanine with formaldehyde in concentrated hydrochloric acid (6,7). However, racemization of about 30% occurs during this reaction (8).…”

“…7-Hydroxy-1,2,3,4-tetrahydroisoquinoline-3 -carboxylic acid [Tic(OH] cannot be prepared directly via cyclization of tyrosine with formaldehyde. Owing to the higher reactivity of hydroxylic ortho-positions, only resinous polycondensation products were isolated (7). Tic(0H) can, however, be synthesized either by a tedious multistep procedure (1 I) or simply via cyclization of 3' ,5' -dibromotyrosine followed by catalytic debromination (12).…”

dc Polarographic Determination of Hydroxylaminoeverninomicin D

“…The chemical (5) or electrochemical (6) reduction of the tertiary nitro group in I yields hydroxylaminoeverninomicin D (11). Nitrosoeverninomicin D (III), undergoing similar reductions, also yields 11.…”