Chirale 2‐Benzopyran‐3‐carbonsäure‐Derivate durch Oxa‐Pictet‐Spengler‐Reaktion von (S)‐3‐Phenylmilchsäure‐Derivaten

Abstract

Chiral 2-Benzopyran-3-carboxylates by Oxa-Pictet-Spengler Reaction of (9-3-Phenyllactic Acid DerivativesStarting with (S)-tyrosine, the methyl (S)-3-(3,4-dihydroxy-carboxylates 16 and 19. On the other hand, the oxa-Pictetpheny1)lactate (15 b) was prepared by acylation, desaminationSpengler reaction of the aryl unsubstituted (S)-3-phenyllactic and Dakin oxidation. The phenyl moiety of 15b was suffi-acid (6) succeeds only with aromatic aldehydes. It was shown ciently activated for the reaction with aromatic and aliphatic that the enantiomeric purity of the compounds 13, 14, 15, 16 aldehydes and ketones to yield the alkyl(3S)-2-benzopyran-3-and 19 was greater than 96% ee.

Synthesis of Oxacycles Employing the Oxa‐Pictet–Spengler Reaction: Recent Developments and New Prospects

“…The reaction name was coined by Wünsch and coworkers in 1992; [13] however, syntheses of isochroman itself and isochroman derivatives employing this strategy have carried out long before and the reaction conditions have been the subject of continuous improvement.…”

The Oxa‐Pictet–Spengler Reaction: A Highlight on the Different Efficiency between Isochroman and Phthalan or Homoisochroman Derivative Syntheses

“…The obtained oil product was purified on silica gel (CHCl 3 , 1 H, 5a-H), 3.17 (m,1 H, 5b-H), 3.97 (m, 1 H, 3a-H), 4.32 (m, 1 H, 3b-H …”

“…This onepot synthesis is based on a modified oxa-Pictet-Spengler reaction, [3][4][5] in which the aromatic carbon atom involved in the heterocyclic ring closure is strongly activated by a para-hydroxy or a para-methoxy functionality and thus acts as a nucleophile. Here we report the synthesis of 1-substituted hydroxyphthalans and 1-substituted hydroxyhomoisochromans performed by the same reaction in order to verify if this synthetic pathway could still be successfully applied to obtain different heterocyclic ring structures.…”

Elaboration of the Isochromane System of Stephaoxocanes Employing an Oxa-Pictet Spengler Type Cyclization

“…They are the source of many interesting natural products, among them the stephaoxocanes, a small family of tetracyclic isoquinoline alkaloids with only a few known members [1].The interesting structural characteristics of these natural products in relationship with our research work [2] prompted us to study the elaboration of models for the total synthesis of natural stephaoxocanes, particularly stephaoxocanidine (1).In this communication, we report the elaboration of isochromanone 2 starting from commercially available m-anisaldehyde (3), following an Oxa-Pictet-Spengler type strategy [3].As shown in the Scheme, bromination of 3 with bromine in AcOH provided bromoaldehyde 4, which olefination under Wittig conditions gave olefins 5. Next, dihydroxylation of the double bond followed by transacetalization of the resulting diol with acetal furnished acetal 7, which TiCl 4 pro- …”

“…In this communication, we report the elaboration of isochromanone 2 starting from commercially available m-anisaldehyde (3), following an Oxa-Pictet-Spengler type strategy [3].…”