One-pot synthesis of cinnamylamines with various protecting groups from cinnamyl ethers

Synthesis and evaluation of ent-Conduramine C-1 derivatives as α-glucosidase inhibitors via CSI-mediated amination reaction

Concise synthesis of ent-conduramine C-1 and its derivatives has been achieved by using commercially available d-ribose. The key steps in the synthesis are regioselective and diastereoselective amination of polybenzyl ethers by chlorosulfonyl isocyanate (CSI), chelation-controlled carbonyl addition, and intramolecular olefin metathesis. All of the synthesized compounds were evaluated for inhibitory activity against α-glucosidase. The derivatives 18 (IC₅₀ = 0.65 ± 0.03 mM) and 19 (IC₅₀ = 0.26 ± 0.01 mM) were identified to be more potent than well-known α-glucosidase inhibitor acarbose (IC₅₀ = 1.05 ± 0.17 mM) as a positive control.

Two-Phase Dibromocyclopropanation of Unsaturated Alcohols Using Flow Chemistry

Dibromocyclopropanations are conventionally done by addition of dibromocarbene to alkenes under phase-transfer conditions in batch reactions using a strong base (50% NaOH (aq)), vigorous stirring and long reaction times. We have shown that cyclopropanation of unsaturated alcohols can be done under ambient conditions using continuous flow chemistry with 40% (w/w) NaOH (aq) as the base. The reactions were generally rapid; the yields were comparable to yields reported in the literature for the conventional batch reaction

Synthesis of (2R,5S)-dihydroxymethyl-(3R,4R)-dihydroxypyrrolidine (DGDP) via stereoselective amination using chlorosulfonyl isocyanate

A stereoselective approach for synthesizing (2R,5S)-dihydroxymethyl-(3R,4R)-dihydroxypyrrolidine 1 (2,5-dideoxy-2,5-imino-d-glucitol, DGDP) was achieved using a seven-step approach starting from 2,3,4,6-tetra-O-benzyl-d-mannose (7). Key steps for the preparation of the title compound 1 involved the regioselective and diastereoselective amination of the cinnamyl anti-1,2-polybenzyl ethers 5 and 6 using chlorosulfonyl isocyanate (CSI) and ring cyclization to form the pyrrolidine ring. The reaction between anti-1,2-polybenzyl ether 5 and CSI in toluene at 0 degrees C afforded the corresponding anti-1,2-amino alcohol 4 as a major product with a diastereoselectivity of 16:1 in 76% yield. The mechanism underlying these reactions may be explained by the neighboring-group effect leading to the retention of stereochemistry.

Diastereoselective synthesis of unsaturated 1,4-amino alcohols as a biologically important moiety

The diastereoselective synthesis of unsaturated 1.4-amino alcohols can be achieved using chial allylic ethers with a hydroxyl group attached to the pi-system and chlorosulfonyl isocyanate. The enantioselectivity of the CSI reaction with the chiral allylic and benzylic ethers was examined in various solvents and temperatures. Based on these results, it was proposed that the CSI reaction is a competitive reaction of a SNi (retention) and a SN1 mechanism (racemization) according to the stability of the carbocation intermediate. This means that there is a greater proportion of retention with the less stable the carbocation intermediate and vise versa.

Mechanism studies on the csi reaction with allyl ethers by varyingp-substituent

We examined the effect of p-substituents in p-substituted cinnamyl methyl ethers and 1-(p-substituted phenyl)allyl methyl ethers with CSI, and confirmed that the CSI reaction of allyl ethers (p-substituted ethers) is a competitive reaction of S(N)i and S(N)1 mechanism according to the stability of the carbocation. And, the only terminal allylic amine was obtained through the migration reaction in thermodynamic reaction condition.