Absolute Stereochemical Assignment of SCH 71450, a Selective Dopamine D4Receptor Antagonist, Through Enantioselective Epimer Synthesis

Synthesis and Detailed Examination of Spectral Properties of (S) and (R)-Higenamine 4'-O-β-d-Glucoside and HPLC Analytical Conditions to Distinguish the Diastereomers

Higenamine is a tetrahydroisoquinoline present in several plants that has β-adrenergic receptor agonist activity. Study of the biosynthesis of higenamine has shown the participation of norcoclaurine synthase, which controls the stereochemistry to construct the (S)-isomer. However, when isolated from nature, higenamine is found as the racemate, or even the (R)-isomer. We recently reported the isolation of higenamine 4'-O-β-d-glucoside. Herein, its (R)- and (S)-isomers were synthesized and compared to precisely determine the stereochemistry of the isolate. Owing to their similar spectral properties, determination of the stereochemistry based on NMR data was considered inappropriate. Therefore, a high-performance liquid chromatography method was established to separate the isomers, and natural higenamine 4'-O-β-d-glucoside was determined to be a mixture of isomers.

Asymmetric Synthesis of Isoquinoline Alkaloids: 2004-2015

In the past decade, the asymmetric synthesis of chiral nonracemic isoquinoline alkaloids, a family of natural products showing a wide range of structural diversity and biological and pharmaceutical activity, has been based either on continuation or improvement of known traditional methods or on new, recently developed, strategies. Both diastereoselective and enantioselective catalytic methods have been applied. This review describes the stereochemically modified traditional syntheses (the Pictet-Spengler, the Bischler-Napieralski, and the Pomeranz-Fritsch-Bobbitt) along with strategies based on closing of the nitrogen-containing ring B of the isoquinoline core by the formation of bonds between C₁-N₂, N₂-C₃, C₁-N₂/N₂-C₃, and C₁-N₂/C₄-C_4a atoms. Methods involving introduction of substituents at the C1 carbon of isoquinoline core along with syntheses applying various biocatalytic techniques have also been reviewed.

Higenamine 4'-O-β-d-glucoside in the lotus plumule induces glucose uptake of L6 cells through β2-adrenergic receptor

Hypoglycemic effect is an efficient means to modulate elevated blood glucose levels in patients with diabetes. We found that the extract of lotus plumule (the germ of Nelumbo nucifera Gaertn. seed) showed potent glucose uptake enhancement activity against L6 myotubes, which results in a hypoglycemic effect. This activity was further investigated, and an active constituent was identified as a single bioactive compound, higenamine 4'-O-β-d-glucoside. Mechanistic studies employing phosphatidylinositol 3-kinase (PI3K) inhibitor, AMP-activated protein kinase (AMPK) inhibitor, or adrenergic receptor antagonist showed that the compound induced its activity through β2-adrenergic receptor. Patients with type II diabetes mellitus frequently develop insulin resistance. Owing to the differences between the mechanism of action of insulin and of the isolated compound, the compound or lotus plumule itself may have the possibility of modulating blood glucose levels in insulin-resistant patients effectively.