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Biomedical subjects

Yogesh S Sanghvi

Publications and source records attributed to Yogesh S Sanghvi.

At least 19 recordsLinked to original sources
PubMed2006

New concept for the separation of an anomeric mixture of alpha/beta-D-nucleosides through regioselective enzymatic acylation or hydrolysis processes.

An efficient and high yield protocol for the synthesis and separation of 3'- and/or 5'-protected alpha-2'-deoxynucleosides has been developed through regioselective acylation/deacylation processes catalyzed by enzymes. Pseudomonas cepacia lipase (PSL-C) was found to be highly chemo- and regioselective toward the 3'-position of the beta-2'-deoxynucleoside derivatives, whereas PSL-C displayed opposite selectivity toward the 5'-position for the corresponding alpha-anomer. The successful application of this protocol was demonstrated by a convenient separation of an alpha/beta-mixture of thymidine derivatives from an industrial waste stream. Furthermore, this technique was also applied for the separation of an anomeric mixture of 2'-deoxy-2'-fluoro-alpha/beta-arabinonucleosides that are useful building blocks for the antisense constructs.

Acylation↗
PubMed2005

Polymer supported carbodiimide strategy for the synthesis of N-acylated derivatives of deoxy- and ribo purinenucleosides using active esters.

A cost-effective synthetic strategy has been used for the selective protection of the exocyclic amino function of purine nucleosides. Instead of using the common protecting groups in their chloride or anhydride forms, the less expensive and nontoxic acidic form was chosen. The acids were first activated to an active ester form using DCC and further successfully used for N-acylation of purine nucleosides. The contamination of the N-acylated product with DCU was inconvenient and was avoided by use of polymer supported-carbodiimide that has the additional advantage of reusability.

Acylation↗
PubMed2005

'Green' methodology for efficient and selective benzoylation of nucleosides using benzoyl cyanide in an ionic liquid.

Benzoyl cyanide in the ionic liquid 1-methoxyethyl-3-methylimidazolium methanesulfonate has been employed as a 'green' alternative and mild reaction condition protocol to conventional pyridine-benzoyl chloride system for efficient and selective benzoylation of nucleosides (of both the ribo- and deoxyribo-series) at ambient temperatures. The use of benzoyl cyanide-ionic liquid combination has been successfully extended for highly efficient benzoylation of phenols, aromatic amines, benzyl alcohol, aliphatic diols, 3-aminophenol and 2-aminobenzylalcohol, which indicates the versatility of this benzoylating system.

Benzoates↗
PubMed2005

One-pot synthesis of TBMPS (bis [tert-butyl)-1 pyrenylmethyl-silyl) chloride as a novel fluorescent silicon-based protecting group for protection of 5'-OH nucleosides and its use as purification handle in oligonucleotide synthesis.

An efficient and novel synthesis of bis(tert-butyl)- 1-pyrenylmethyl-silyl group (TBMPS) has been reported having fluorescent properties conferred by the pyrenyl group. This silyl group being base labile is efficiently used for one-pot protection of the 5-OH of the nucleosides. While incorporated terminally at the 5-OH of long sequences viz. AA TGG AGC CAG T and GC TAT GTCAGT TCC CCT TGG TTC TC, this group is also helpful in subsequent purification by HPLC as well as PAGE. Besides these, a labeled dimer (T*T) and a labeled tetramer (T*TTT) were also synthesized to compare the fluorescence properties of short and long labeled sequences. Fluorescence properties of these sequences were studied in detail to find the suitability of the approach.

Biochemistry↗
PubMed2005

A solid supported reagent for internucleoside H-phosphonate linkage formation.

A fast and convenient procedure for synthesis of dinucleoside H-phosphonates is obtained through use of the novel polystyrene supported 5-carboxy-5-methyl-2-oxo-2-chloro-1,3,2-diaoxaphosphorinane reagent. Virtually quantitative H-phosphonate condensations are obtained leading to excellent isolatedyields and with only a simple filtration as the purification procedure. This provides for a convenient and high-yielding procedure that should be suited for solution-phase synthesis of oligonucleotides.

Indicators and Reagents↗
PubMed2005

Mild, efficient, selective and "green" benzoylation of nucleosides using benzoyl cyanide in ionic liquid.

Use of benzoyl cyanide (BzCN) for benzoylation of nucleosides has been studied, both in pyridine and in ionic liquid BzCN in 1-methoxyethyl-3-methylimidazolium methanesulfonate as ionic liquid has been found to be a "green "alternative compared to the pyridine-BzCN system. An efficient and selective benzoylation of nucleosides of both, the 2'-deoxy- and the ribo-series at ambient temperature was accomplished.

Cyanides↗
PubMed2005

Dimethylthiarum disulfide: new sulfur transfer reagent in phosphorothioates oligonucleotide synthesis.

Dimethylthiarum disulfide (DTD) has been developed as a new and efficient sulfur-transfer reagent for automated synthesis of phosphorothioate oligonucleotides using phosphoramidite chemistry. The traditional four-step automated oligonucleotide synthesis has been compressed to three-step protocol using DTD. This improvement allowed an overall 20% reduction in the solvent consumption and reduced the total synthesis time by 25%. The large-scale application of DTD has been successfully demonstrated by synthesis of therapeutically useful 20-mer phosphorothioate antisense oligonucleotides with excellent yield and purity.

Base Sequence↗
PubMed2004

Regioselective enzymatic acylation of beta-L-2'-deoxynucleosides: application in resolution of beta-D/L-2'-deoxynucleosides.

[reaction: see text] A practical synthesis of beta-L-3'- and beta-L-5'-O-levulinyl-2'-deoxynucleosides has been described for the first time through enzymatic acylation and/or hydrolysis processes. It is noteworthy that the different behavior exhibited by Pseudomonas cepacia lipase in the acylation of D- and L-nucleosides allows the parallel kinetic resolution of D/L-nucleosides.

Acylation↗
PubMed2004

Synthesis of 2'-substituted MMI linked nucleosidic dimers: an optimization study in search of high affinity oligonucleotides for use in antisense constructs.

The synthesis of a series of methylene(methylimino) (MMI) linked oligodeoxyribonucleotide dimers modified at the 2'-position with fluoro and/or methoxy groups and their incorporation into different sequences has been accomplished. From these dimers, bis 2'-OMe MMI dimer was selected for further studies based on its synthetic accessibility and the increased thermodynamic stability conferred upon oligonucleotides incorporating this modification.

DNA, Antisense↗
PubMed2004

Therapeutic oligonucleotides: the state-of-the-art in purification technologies.

Currently, there are over 40 oligonucleotide-based pharmaceutical products in various stages of clinical development for the treatment of an assortment of life-threatening diseases. As a result, the production of synthetic oligonucleotides has become increasingly important, with applications in antisense-, aptamer-, ribozyme-, immunostimulatory CpG molecule- and RNAi-related therapeutics. Due to the enormous commercial interest in these technologies, the manufacturing and purification processes for oligonucleotide production have been furtive and practiced in a confidential environment. As a result, limited information on large-scale processing is available in the scientific literature. The purpose of this article is to review the current state-of-the-art in oligonucleotide purification technologies, which have resulted in drug products meeting stringent therapeutic specifications. An indication of new and emerging purification technologies, including simulated moving bed- and membrane-based separation, is given.

Chromatography↗
PubMed2003

Novel synthesis of 2'-O-methylguanosine.

An efficient and chemoselective synthesis of 2'-O-methylguanosine (6) has been accomplished in high yield without protection of the guanine base. The salient feature of the synthesis of 6 lies in the application of methylene-bis-(diisopropylsilyl chloride), (MDPSCl(2), 2) as a new 3',5'-O-protecting group for nucleosides. Use of CH(3)Cl as a weak electrophile and NaHMDS as a mild base was crucial to the success of the 2'-O-methylation of 3',5'-O-protected guanosine.

Guanosine↗
PubMed2002

Synthesis of 2'-O-methoxyethylguanosine using a novel silicon-based protecting group.

A short and efficient synthesis of 2'-O-methoxyethylguanosine (8) is described. Central to this strategy is the development of a novel silicon-based protecting group (MDPSCl(2), 2) used to protect the 3',5'-hydroxyl groups of the ribose. Silylation of guanosine with 2 proceeded with excellent regioselectivity and in 79% yield. Alkylation of the 2'-hydroxyl group of 6 proceeded with methoxyethyl bromide and NaHMDS and afforded compound 7 in 85% yield, without any noticeable cleavage of the silyl protecting group and without the need to protect the guanine base moiety. Finally, deprotection of 7 was achieved using TBAF and produced 8 in 97% yield.

Alkylation↗
PubMed2002

Building blocks for the solution phase synthesis of oligonucleotides: regioselective hydrolysis of 3',5'-Di-O-levulinylnucleosides using an enzymatic approach.

A short and convenient synthesis of 3'- and 5'-O-levulinyl-2'-deoxynucleosides has been developed from the corresponding 3',5'-di-O-levulinyl derivatives by regioselective enzymatic hydrolysis, avoiding several tedious chemical protection/deprotection steps. Thus, Candida antartica lipase B (CAL-B) was found to selectively hydrolyze the 5'-levulinate esters, furnishing 3'-O-levulinyl-2'-deoxynucleosides 3 in >80% isolated yields. On the other hand, immobilized Pseudomonas cepacia lipase (PSL-C) and Candida antarctica lipase A (CAL-A) exhibit the opposite selectivity toward the hydrolysis at the 3'-position, affording 5'-O-levulinyl derivatives 4 in >70% yields. A similar hydrolysis procedure was successfully extended to the synthesis of 3'- and 5'-O-levulinyl-protected 2'-O-alkylribonucleosides 7 and 8. This work demonstrates for the first time application of commercial CAL-B and PSL-C toward regioselective hydrolysis of levulinyl esters with excellent selectivity and yields. It is noteworthy that protected cytidine and adenosine base derivatives were not adequate substrates for the enzymatic hydrolysis with CAL-B, whereas PSL-C was able to accommodate protected bases during selective hydrolysis. In addition, we report an improved synthesis of dilevulinyl esters using a polymer-bound carbodiimide as a replacement for dicyclohexylcarbodiimide (DCC), thus considerably simplifying the workup for esterification reactions.

Burkholderia cepacia↗
PubMed2002

Tandem oligonucleotide synthesis on solid-phase supports for the production of multiple oligonucleotides.

More than one oligonucleotide can be synthesized at a time by linking multiple oligonucleotides end-to-end in a tandem manner on the surface of a solid-phase support. The 5'-terminal hydroxyl position of one oligonucleotide serves as the starting point for the next oligonucleotide synthesis. The two oligonucleotides are linked via a cleavable 3'-O-hydroquinone-O,O'-diacetic acid linker arm (Q-linker). The Q-linker is rapidly and efficiently coupled to the 5'-OH position of immobilized oligonucleotides using HATU, HBTU, or HCTU in the presence of 1 equiv of DMAP. This protocol avoids introduction of phosphate linkages on either the 3'- or 5'-end of oligonucleotides. A single NH(4)OH cleavage step can simultaneously release the products from the surface of the support and each other to produce free 5'- and 3'-hydroxyl termini. Selective cleavage of one oligonucleotide out of two sequences has also been accomplished via a combination of succinyl and Q-linker linker arms. Tandem synthesis of multiple oligonucleotides is useful for producing sets of primers for PCR, DNA sequencing, and other diagnostic applications as well as double-stranded oligonucleotides. Tandem synthesis of the same sequence multiple times increases the yield of material from any single synthesis column for maximum economy in large-scale synthesis. This method can also be combined with reusable solid-phase supports to further reduce the cost of oligonucleotide production.

Base Sequence↗