4-Keto-1,2,3,4-tetrahydroisoquinolines

Kai-ho-chien 775 Ketodihydromethylmorphimethine, 235 l-Keto-6 7-dimethoxy-2-methyI-tetrahydroisoquinoline, 354 Ketohydroxycassanic acid, 728, 729, 730 Ketohydroxycassenic acid. See Cassaic acid, 728... 

Peroxidase and laccase enzymes were used to catalyze the decarboxylation of various tetrahydroisoquinoline-1-carboxylic acids to give high yields of the corresponding 3,4-dihydroisoquinolines (204). Compounds such as 125 (Scheme 29) are derived from Pictet-Spengler ring closure via a-keto acid and aryl amine condensation and are of biogenetic importance. The possible relevance of iso-... 

The 4-keto-l,2,3,4-tetrahydroisoquinolines are more systematically called 2,3-dihydro-4(l.ff J-isoquinolones, but the keto nomenclature would seem to be more descriptive of their properties. 

Synthesis of i-Keto-, 2,3,4 -tetrahydroisoquinolines These ketones have been prepared by four different routes a Dieck-mann condensation [Eq. (22)], ring closure of benzylglycine derivatives [Eq. (23)], ring closure of substituted nitriles [Eq. (24)], and a Grignard reaction on 4-hydroxy-JV-alkylisoquinolinium salts [Eq. (25)]. Earlier unsuccessful attempts at their synthesis have been summarized.52,58... 

In Tables I and II, the known types of 4-acetoxy-, 4-alkoxy-, and 4-hydroxy-l,2,3,4-tetrahydroisoquinolines are indicated. Table III summarizes the known 4-keto-l,2,3,4-tetrahydroisoquinolines. In Tables IV and V, the various classes of 1,2,3,4-tetrahydroisoquinolines and aromatic isoquinolines which have been made by the methods discussed in this article are given. In Tables VI and VII, the 4-phenyl-l,2,3,4-tetrahydroisoquinolines and bicyclic compounds made by nucleophilic displacement of the 4-hydroxy group are summarized. Twenty-four compounds e.g., (31-40) prepared from 30 with active CH,78 NH, and SH77 compounds have been reported details may be found in the references cited. 

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