Solution Oligonucleotide APIs: Regulatory Considerations.

Manufacture of oligonucleotide active pharmaceutical ingredients (APIs) typically consists of solid-phase synthesis, deprotection and cleavage, purification and filtration, and isolation from aqueous solutions through lyophilization. In the first step of drug product manufacture, the API is dissolved in water again and excipients are added. While isolation of oligonucleotide APIs can be meaningful in many cases, there may be cases where keeping the API in solution provides benefit, and multiple technical aspects must be taken into account and balanced when determining the appropriate API form. A significant factor is whether an API in solution will contain additional components. While APIs in solution containing additional components (so-called formulated APIs) are well established for biological products, there are regulatory guidelines in place that represent hurdles for industry to using a formulated API approach for oligonucleotide drugs. The present communication outlines conditions where a formulated API approach can be chosen in compliance with existing guidelines. Relevant aspects pertaining to risk management, GMP standards, facility design, control strategies, and regulatory submission content are discussed. In addition, the authors propose that existing guidelines be modernized to enable the use of a formulated API approach for additional reasons than the ones described in the existing regulatory framework. The manuscript aims to promote a dialog with regulators in this field.

Asymmetric syntheses of (-)-3-epi-Fagomine, (2R,3S,4R)-dihydroxypipecolic acid, and several polyhydroxylated homopipecolic acids.

A range of enantiopure polyhydroxylated piperidines, including (2R,3S,4R)-dihydroxypipecolic acid, (-)-3-epi-fagomine, (2S,3S,4R)-dihydroxyhomopipecolic acid, (2S,3R,4R)-dihydroxyhomopipecolic acid, and two trihydroxy-substituted homopipecolic acids, have been prepared using diastereoselective olefinic oxidations of a range of enantiopure tetrahydropyridines as the key step. The requisite substrates were readily prepared from tert-butyl sorbate using our diastereoselective hydroamination or aminohydroxylation protocols followed by ring-closing metathesis. After diastereoselective olefinic oxidation of the resultant enantiopure tetrahydropyridines and deprotection, enantiopure polyhydroxylated piperidines were isolated as single diastereoisomers (>99:1 dr) in good overall yield.

Asymmetric syntheses of methyl N,O-diacetyl-D-3-epi-daunosaminide and methyl N,O-diacetyl-D-ristosaminide.

Ab initio asymmetric syntheses of methyl N,O-diacetyl-D-3-epi-daunosaminide and methyl N,O-diacetyl-D-ristosaminide, employing diastereoselective epoxidation and dihydroxylation, respectively, of alkyl (3S,αR,Z)-3-[N-benzyl-N-(α-methylbenzyl)amino]hex-4-enoates as the key steps, are reported. The requisite substrates were readily prepared using the conjugate additions of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to methyl and tert-butyl (E)-hexa-2-en-4-ynoates followed by diastereoselective alkyne reduction. syn-Dihydroxylation using OsO4 proceeded under steric control on the 4Re,5Re face of the olefin to give the corresponding diol, which subsequently underwent lactonization. Meanwhile, epoxidation using F3CCO3H in conjunction with F3CCO2H proceeded on the opposite 4Si,5Si face of the olefin under hydrogen-bonding control from the in situ formed ammonium ion. Treatment of the intermediate epoxide with concd aq H2SO4 promoted highly regioselective ring-opening (distal to the in situ formed ammonium moiety) to give the corresponding diol (completing overall the formal anti-dihydroxylation of the olefin), which then underwent lactonization under the reaction conditions. Elaboration of these diastereoisomeric lactones through hydrogenolysis, N-Boc protection, reduction, methanolysis, and acetate protection gave methyl N,O-diacetyl-D-3-epi-daunosaminide and methyl N,O-diacetyl-D-ristosaminide.

Room-temperature palladium-catalyzed C-H activation: ortho-carbonylation of aniline derivatives.

Pd and CO--ureally got me! The title reaction proceeds efficiently at 18 degrees C under CO (1 atm) with 5 % [Pd(OTs)(2)(MeCN)(2)] as precatalyst. Depending on the solvents used, either anthranilates or cyclic imides can be obtained in high yields (see picture, BQ = benzoquinone, Ts = 4-toluenesulfonyl).

Distinct reactivity of Pd(OTs)2: the intermolecular Pd(II)-catalyzed 1,2-carboamination of dienes.

A Pd-catalyzed intermolecular 1,2-carboamination route to indolines from N-aryl ureas and 1,3-dienes that proceeds under mild conditions in relatively nonacidic media, is presented. The in situ generation, or preformation, of a palladium tosylate emerges as a key parameter in gaining the requisite reactivity for the C-H insertion/carbopalladation/nucleophilic displacement process.

Chirality transfer in the aza-[2,3]-Wittig sigmatropic rearrangement.

The aza-[2,3]-Wittig sigmatropic rearrangements of substrates derived from enantiomerically pure alanine, valine and serine with phenyl and ester anion stabilising groups were investigated for their efficiency in chirality transfer. It was found that a methyl substituent at the stereogenic centre of the rearrangement precursors was inadequate to control the alkene stereoselectivity and enantioselectivity of the rearrangement. Ester stabilised anions of valine and serine derivatives were the most successful with up to 66% yield, 14 : 1 alkene (E)-stereoselection and 88% chirality transfer. A limitation to the steric bulk of the stereogenic centre was noted in that the substituent has to be bulky enough to dictate alkene stereoselection, but not too large to compromise the directing effect of the activating phenyldimethyl silyl substituent on the anion stabilising group. Experimental evidence suggested a possible complimentary coordinating effect of an O-MOM serine substituent, which may assist alkene stereoselectivity and enantioselectivity.