Mild and reliable cleavage sequence for phenoxy acetates

A novel combination of reliable transformations like ester saponification and subsequent Curtius-rearrangement employing mild reaction conditions, offers the first synthetically interesting strategy for the removal of methoxycarbonylmethyl groups from phenolic oxygens. This methodology gives also access to labile iodosubstituted phenols.     

A new method for the cleavage of nitrobenzyl amides and ethers

A mild and efficient o- and p-nitrobenzyl cleavage protocol was developed. o- and p-nitrobenzyl groups were easily removed from a variety of substrates using 20% aqueous NaOH in methanol at 75 °C, presumably via oxidation at the benzylic position by oxygen dissolved in the solution. These easily introducible and removable nitrobenzyl groups can serve as valuable protecting groups for the synthesis of multifunctional, complex molecules.     

Concise and efficient synthesis of 3′-O-triphosphates of 2′-deoxyadenosine and 2′-deoxycytidine

We describe concise and efficient synthesis of 2′-deoxyadenosine-3′-O-triphosphate (2′-d-3′-ATP) and 2′-deoxycytidine-3′-O-triphosphate (2′-d-3′-CTP) which are well known for their various biological applications. One-pot synthetic methodology was used to convert N⁶-Benzoyl-5′-O-levulinoyl-2′-deoxyadenosine into N⁶-Benzoyl-5′-O-levulinoyl-2′-deoxyadenosine-3′-O-triphosphate in 72% yield. One-step concurrent deprotection of N⁶-Benzoyl and 5′-O-levulinoyl groups using concentrated aqueous ammonia resulted in 2′-d-3′-ATP in 75% yield. The same synthetic strategy was successfully employed to convert N⁴-Benzoyl-5′-O-levulinoyl-2′-deoxycytidine into 2′-d-3′-CTP in 66% yield.     

2‐[Dimethyl(2‐naphthylmethyl)silyl]ethoxy Carbonate (NSEC) as a New Mode of Hydroxyl Group Protection*

2‐[Dimethyl(2‐naphthylmethyl)silyl]ethoxy carbonate (NSEC) is a novel protecting group to mask hydroxyl groups. NSECCl is available in three steps from chlorodimethylvinylsilane and 2‐(bromomethyl)naphthalene. Introduction and removal of the NSEC group are performed easily and rapidly in the presence of most protecting groups currently used in carbohydrate chemistry. The removal of NSEC can be carried out under mild conditions in the presence of various ether and ester protecting groups. Additionally, the NSEC group is stable to glycosylation conditions using glycosyl phosphates. The synthesis of disaccharide 18 containing NSEC has been accomplished.     

An efficient and chemoselective deprotection of aryl- and styrenyldithioketals (acetals)

In this Letter, an efficient and chemoselective deprotection of aryl- and styrenyldithioketals (acetals) is described. After being carefully examined, 10% Pd/C and Amberlite 120 in refluxing methanol was found to be an excellent condition for the chemoselective deprotection of aryl- and styrenyldithioketals (acetals) in good yields. Under this condition, no deprotection and no reduction of alkyldithioketals (acetals) was observed.     

P2O5/SiO2 as an Efficient Reagent for Selective Deprotection of 1,1‐Diacetates under Solvent‐Free Conditions

A mild and efficient method has been developed for the selective deprotection of 1,1‐diacetates of aldehydes in excellent yields by means of the P₂O₅/SiO₂ reagent. Advantages of this method are the use of inexpensive and selective reagent, with high yields in simple operation, and short reaction time under solvent‐free conditions.     

2,6-Dicarboxypyridinium Chlorochromate. An Efficient and Selective Reagent for the Mild Deprotection of Acetals, Thioacetals, and 1,1-Diacetates to Carbonyl Compounds

Summary. 2,6-Dicarboxypyridinium chlorochromate (2,6-DCPCC) was found to be an efficient reagent for the conversion of acetals, thioacetals, and 1,1-diacetates to their corresponding carbonyl compounds under neutral and anhydrous conditions in good to excellent yields. Selective deprotection of acetals or 1,1-diacetates in the presence of thioacetals at room temperature is also observed with this reagent.     

Host (nanocavity of zeolite-Y)–guest (molybdophosphoric acid) nanocomposite materials: An efficient catalyst for solvent-free synthesis and deprotection of 1,l-diacetates

In the present work, a mild and efficient method has been developed for the synthesis of acylals from aldehydes with acetic anhydride in the presence of molybdophosphoric acid encapsulated into dealuminated zeolite Y (MPA-DAZY) as a catalyst under solvent-free conditions at 45–55 °C in good to excellent yield. The deprotection of acylals has also been attained using this catalyst in acetonitrile. The catalyst was reused several times without efficient loss of its catalytic activity.     

Base-promoted regioselective synthesis of 1,2,3,4-terahydroquinolines and quinolines from N-boc-3-piperidone

An efficient synthesis of 1,2,3,4-tetrahydroquinolines with donor and acceptor group has been delineated by base mediated ring transformation of 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles by N-boc-3-piperidone followed by consecutive deprotection of Boc group under acidic conditions. This reaction involves 2 new bond formations namely C4a-C5 and C8a-C8 in order to create the nucleus. Various donor and acceptor functional groups like aryl, heteroaryl, nitrile, methylsulfanyl and secondary amine were installed in 1,2,3,4-tetrahydroquinolines. We extended our approach to synthesize the fused 1,2,3,4-tetrahydroquinolines by using 2-oxobenzo[h]chromenes as precursor. Further, we synthesized fused and isolated quinolines through aromatization of 1,2,3,4-tetrahydroquinolines by DDQ in excellent yields. Single-crystal X-ray analysis of the Boc protected tetrahydroisoquinoline 6t showed the steric hindrance between N-Boc and aryl group.     

A simple and efficient synthesis of (±)-mesembrine

A simple and efficient synthesis of (±)-mesembrine 1 is described employing double Michael addition and as the key step in 18% overall yield.