A new synthetic route to (North)-methanocarba nucleosides designed as A3 adenosine receptor agonists.
ABSTRACT Activation of the A3 adenosine receptor (AR) is associated with cerebroprotective, cardioprotective, and anticancer effects. Among potent and selective A3 AR agonists are novel methanocarba adenosine analogues in which the conformation of a pseudo-ribose moiety is locked in the North (N) hemisphere of the pseudorotational cycle. 5'-Uronamide (N)-methanocarba nucleosides, such as MRS1898 and MRS2346, are examples of full agonists of the human A3 AR. An improved convergent approach from easily accessible 2,3-O-isopropylidene-d-erythrose (2b), and the combination of a strategic intramolecular cyclopropanation step plus the acid-catalyzed isomerization of an isopropylidene group, provided a suitable pseudosugar precursor (23) for the synthesis of MRS1898, MRS2346, and related analogues. This new synthetic route uses readily available building blocks and opens the way for the preparation of a variety of targets on a reasonable scale.
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ABSTRACT: Adenosine receptors (ARs) and P2Y receptors for purine and pyrimidine nucleotides have widespread distribution and regulate countless physiological processes. Various synthetic ligands are in clinical trials for treatment of inflammatory diseases, pain, cancer, thrombosis, ischemia, and other conditions. The methanocarba (bicyclo[3.1.0]hexane) ring system as a rigid substitution for ribose, which maintains either a North (N) or South (S) conformation, tends to preserve or enhance the potency and/or selectivity for certain receptor subtypes. This review summarizes recent developments in the synthetic approaches to these biologically important nucleoside and nucleotide analogues.Medicinal Chemistry Communication 03/2013; 4(4):619-630. DOI:10.1039/C2MD20348K · 2.63 Impact Factor
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ABSTRACT: Enantiopure 3,6-dihydro-2H-1,2-oxazines were prepared by [3+3] cyclisations starting from lithiated methoxyallene and the L-erythrose-derived nitrones 1′ and 3. The role of the side-chain protective group, which steers the highly selective formation of either anti- or syn-configured products, was demonstrated. A hydroboration/oxidation protocol smoothly converted 1,2-oxazine derivative syn-5 into secondary alcohol 6. After deprotection, polyhydroxylated tetrahydro-2H-1,2-oxazine 11, which can be regarded as an azasugar, was isolated. Analogous treatment of 1,2-oxazine anti-5 with the borane not only provided the expected secondary alcohol 7, but it also induced reduction of the C=C bond and ring opening. Treatment of syn-5 and anti-2 with hydrochloric acid in methanol induced deprotections and cyclisations leading to bicyclic tetrahydro-2H-1,2-oxazine derivatives. The second ring can be either a furan or a pyran ring. In the syn series, furan derivative 12 was formed exclusively, and its hydrogenolysis led to enantiopure aminofuran derivative 14. Acid-promoted rearrangement of unprotected anti-2 led to a mixture of bicyclic compounds with furan or pyran rings fused to the 1,2-oxazine core. However, when TBDPS-protected compound 20 was used it cleanly led to 1,2-oxazine 21 with a fused furan ring and then to aminofuran 22. Alternatively, the N–O bond in unprotected anti-2 was chemoselectively reduced with samarium diiodide, efficiently generating highly functionalized allylic alcohol 23. Acid-promoted cyclisation and deprotection furnished furan derivative 24. Mechanistic suggestions to explain the different outcomes of the acid-induced transformations are provided. Overall, it is demonstrated that the stereodivergent addition of lithiated alkoxyallenes to L-erythrose-derived nitrones allow flexible access to a series of enantiopure amino polyols, including aminofuran derivatives.European Journal of Organic Chemistry 06/2012; DOI:10.1002/ejoc.201200158 · 3.15 Impact Factor
Bulletin- Korean Chemical Society 12/2010; 31(12). DOI:10.5012/bkcs.2010.31.12.3788 · 0.84 Impact Factor