Oxa-Spengler Reaction Lab Report

d. Nirav Kapadia and others uses Oxa-pictet-spengler reaction as one of the key steps in the synthesis of new isochroman heterocycles containing a 4, 5, 6a,7-tetrahydrodibenzo[de,g]chromene and further performed the acidic cleavage of molecule to form phenanthrene alkaloids(33).

e. Santosh J. Gharpure et al worked on stereoselective synthesis of oxazino[4,3-a]indoles via oxa-Pictet–Spengler reaction of indoles having N-tethered vinylogous carbonate(26). Furthur optimization of reaction conditions were done and explained in table 19& 20.

Table 19. Scope of the Oxa-Pictet-Spengler reaction for the synthesis of oxazinoindoles

ENTRY R1 R2 R3 PRODUCT YIELD DIASTERIOMER RATIO
1 H H Ph 69l 85 >19:1
2 H H CH2OBn 69a 60 >19:1
3 H ----------(CH2)4-----------

Gobe and team used AuI or AuIII complexes for the synthesis of pentacyclic indolo[2,3-a]quinolizidines from N-allyl tryptamines and ortho-alkynylarylaldehydes(36). They performed this reaction following the novel work done by Adithi Danda et al for the development of a catalytic two-step reaction sequence to access a range of complex heterocyclic frameworks based on biorelevant indole/oxindole scaffolds using Au(1) complex as a catalyst(37). They initiated their study by establishing the suitable catalytic system for the Pictet–Spengler gold-catalyzed cyclization onepot process (Scheme 16). To this aim, N-allyl tryptamine 70 and aldehyde 71 were reacted in the presence of catalytic amounts of diphenyl phosphate (DPP, 5 mol%), to ensure catalysis of the Pictet–Spengler reaction and various catalyst 72 in dichloroethane at

It may limit the application of the PS cyclization as a chemical ligation method for peptides with N-terminal aromatic residue and peptides with aldehyde residue at C-terminal(40).
7. Pictet-spengler reaction for protein chemical modification= proteins are having aldehyde and ketone groups in their structures. So proteins are taken as a substrate and the pictet-spengler reaction is performed for making modification in the chemical nature of the proteins. P. agarwal and co-workers work for protein chemical modification by conducting a pictet-spengler reaction between aldehydes and alkoxyamines. This forms an oxyiminium ion as an intermediate that eventually undergoes intramolecular C-C bond with indole nucleophile to form an oxacarboline product. As compared to the oxime and hydrazone conjugates, the oxacarbolines are very much stable towards the hydrolysis under physiological relevant conditions as depicted by their experiment. In order to use this strategy for site specific chemical modification of formylglycine and glyoxalglycine-functionalized, they use an aldehyde-tagged variant of the Herceptin( a therapeutic monoclonal antibody). All the experiments performed by them showed that the Pictet-spengler reaction has a bright future in the research for the