MDPSCL 2 : A New Protecting Group for Chemoselective Synthesis of 2 0 -O-Alkylated Guanosines

ABSTRACT An improved strategy for the synthesis of 2 0 -O-methyl-guanosine (6) and 2 0 -MOE-guanosine (8) is reported. The regioselectivity of the alkylation was attained using a novel silicon-based protecting group, methylene-bis (diisopropyl-silylchloride) (MDPSCl 2 , 2). The alkylation proceeded in a chemoselective manner using NaHMDS as the base and MeCl or MOE-Br as the appropriate electrophiles

Imine-palladacycles as phosphine-free precatalysts for low temperature Suzuki-Miyaura synthesis of nucleoside analogues in aqueous media

The synthesis and characterization of new water-soluble dinuclear palladacycles of the general formula [{Pd(R-C^N-SO3Na)(μ-AcO)}2] (R = H (1), OMe (2), Cl (3)) incorporating an ortho-metalated sodium 4-(N-benzylideneamino)benzenesulfonate moiety is reported. These complexes have been revealed to be excellent phosphine-free catalysts for the synthesis of functionalized nucleoside analogues involving a low-temperature Suzuki–Miyaura coupling of 5-iodo-2′-deoxyuridine with different arylboronic acids in neat water. The potential of 1–3 as synthetic precursors was also tested, and bridging acetates were cleaved by reaction with neutral PPh3, yielding the corresponding mononuclear derivatives [Pd(R-C^N-SO3Na)(AcO)(PPh3)] (R = H (4), MeO (5), Cl (6)). Analytical and spectroscopic techniques confirmed the proposed formulas and reactivities reported for complexes 1–6. Structural characterization by X-ray diffraction of single crystals grown from samples of 4 and 6 produced the unexpected but valuable crystallization-mediated compounds 4cm and 6cm that also supported the results presented here.This work has been partially supported by RTI2018-098233-B-C21 (MICINN) and 20790/PI/18 (Fundación SENECA CARM) grants. A.R.K would like to acknowledge SERB for EMR grant (EMR/2016/005439). Professor Gregorio Sánchez, who recently passed away, is gratefully acknowledged for his contribution to this work and his wise and continuous advise and suppor

Sustainable Protocol for the Synthesis of 2′,3′-Dideoxynucleoside and 2′,3′-Didehydro-2′,3′-dideoxynucleoside Derivatives

An improved protocol for the transformation of ribonucleosides into 2′,3′-dideoxynucleoside and 2′,3′-didehydro-2′,3′-dideoxynucleoside derivatives, including the anti-HIV drugs stavudine (d4T), zalcitabine (ddC) and didanosine (ddI), was established. The process involves radical deoxygenation of xanthate using environmentally friendly and low-cost reagents. Bromoethane or 3-bromopropanenitrile was the alkylating agent of choice to prepare the ribonucleoside 2′,3′-bisxanthates. In the subsequent radical deoxygenation reaction, tris(trimethylsilyl)silane and 1,1′-azobis(cyclohexanecarbonitrile) were used to replace hazardous Bu3SnH and AIBN, respectively. In addition, TBAF was substituted for camphorsulfonic acid in the deprotection step of the 5′-O-silyl ether group, and an enzyme (adenosine deaminase) was used to transform 2′,3′-dideoxyadenosine into 2′,3′-dideoxyinosine (ddI) in excellent yield

Preparation of a 4′‐Thiouridine Building‐Block for Solid‐Phase Oligonucleotide Synthesis

Starting from a commercially available thioether, we report a nine‐step synthesis of a 4′‐thiouridine phosphoramidite building‐block. We install the uracil nucleobase using Pummerer‐type glycosylation of a sulfoxide intermediate followed by a series of protecting group manipulations to deliver the desired phosphite. Notably, we introduce a 3′,5′‐O‐di‐tert‐butylsilylene protecting group within a 4′‐thiosugar framework, harnessing this to ensure regiospecific installation of the 2′‐O‐silyl protecting group. We envisage this methodology will be generally applicable to other 4′‐thionucleosides and duly support the exploration of their inclusion within related nucleic acid syntheses. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: (2R,3S,4R)‐2,3‐O‐Isopopropylidene‐5‐O‐tert‐butyldiphenylsilyl‐1‐(4‐sulfinyl)cyclopentane: Sulfoxidation Basic Protocol 2: 2′,3′‐O‐Isopropylidene‐5′‐O‐tert‐butyldiphenylsilyl‐4′‐thiouridine: Pummerer glycosylation Basic Protocol 3: 4′‐Thiouridine: Deprotection Basic Protocol 4: 2′‐O‐tert‐Butyldimethylsilyl‐3′,5′‐di‐tert‐butylsiloxy‐4′‐thiouridine: 2′,3′,5′‐O‐silylation Basic Protocol 5: 2′‐O‐tert‐Butyldimethylsilyl‐4′‐thiouridine: Selective 3′‐5′‐desilylation Basic Protocol 6: 2′‐O‐tert‐Butyldimethylsilyl‐5′‐O‐dimethoxytrityl‐4′‐thiouridine: 5′‐O‐dimethoxytritylation Basic Protocol 7: 2′‐O‐tert‐butyldimethylsilyl‐3′‐O‐[(2‐cyanoethoxy)(N, N‐diisopropylamino)phosphino]‐5′‐O‐dimethoxytrityl‐4′‐thiouridine: 3′‐O‐phosphitylatio