134996-50-2Relevant articles and documents
Photocycloaddition of S, S-Dioxo-benzothiophene-2-methanol, Reactivity in the Solid State and in Solution: Mechanistic Studies and Diastereoselective Formation of Cyclobutyl Rings
O'Hara, Chelsea,Yang, Chou-Hsun,Francis, Andrew J.,Newell, Brian S.,Wang, Haobin,Resendiz, Marino J. E.
, p. 9714 - 9725 (2019)
The formation of cyclobutane rings is a promising strategy in the development of potential drugs and/or synthetic intermediates, typically challenging to obtain due to their constrained nature. In this work, the [2 + 2] photocycloaddition reaction of S,S-dioxobenzothiophene-2-methanol was explored in microcrystalline powders and its outcome was compared to that observed in solution. It was found that the molecular constraints inherited within the crystal lattice provide an optimal environment that leads to photodimer 4 as the major product in ca. 9.6:0.4 diastereomeric ratios with conversions >95%. The photoreaction was analyzed via X-ray, displaying a crystalline-to-amorphous transformation and showing that units of monomer 2 align to generate the corresponding dimer with a syn-head-to-tail regio- and diastereoselectivity. This result contrasted with that obtained in solution, where the diastereomeric ratio varied as a function of the excited state that is generated, to yield mixtures of dimers 4 and 5 (anti-head-to-tail), or exclusively 5 in the triplet-sensitized photoreaction, in the presence of benzophenone. Density functional theory was used to elucidate a plausible detailed mechanism for the phototransformation, which aided in justifying the results that led to the corresponding dimers. X-ray crystallography allowed us to establish the stereochemical assignment of the obtained cyclobutyl rings. Thus, the use of solid-state or solution photochemistry can be used to gain control of diastereo- and regioselectivities in the formation of this important moiety.
The 1,1-dioxobenzo[b]thiophene-2-ylmethyloxycarbonyl (Bsmoc) amino- protecting group
Carpino, Louis A.,Ismail, Mohamed,Truran, George A.,Mansour,Iguchi, Shin,Ionescu, Dumitru,El-Faham, Ayman,Riemer, Christoph,Warrass, Ralf
, p. 4324 - 4338 (2007/10/03)
Full details are presented for use of the Bsmoc amino-protecting group for both solid phase and rapid continuous solution syntheses. Application to the latter methodology represents a significant improvement over the corresponding Fmoc-based method for rapid solution synthesis due to the opportunity to use water or saturated sodium chloride solution rather than an acidic phosphate buffer to remove all byproducts, with consequent cleaner phase separation and higher yields of the growing peptide. Comparison of the Bsmoc and Bspoc functions showed that the former, because of steric hindrance, does not suffer from the competitive or premature deblocking observed with the Bspoc system. Because of its in corporation of a styrene chromophore, resin loading of Bsmoc amino acids could be followed as has previously been shown for the Fmoc analogues. Applications of Bsmoc chemistry to peptide sequences incorporating the base sensitive Asp-Gly unit gave less contamination due to aminosuccinimide formation than comparable syntheses involving standard Fmoc chemistry because a weaker or less concentrated base could be used in the deblocking step. Experimental details are presented for building up peptides in solution via the continuous methodology. Deblockings involved the use of insoluble piperazino silica as well as the polyamine TAEA which simplified aqueous separation of the growing, but nonisolated peptide product, from excess acylating agent and other side products formed in the deblocking process. By the appropriate choice of base, one can act selectively at either site of a molecule which incorporates both β- elimination and Michael acceptor sites as protective units (Bsmoc vs Fm and Fmoc vs Bsm).
Reagents for rapid peptide synthesis
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, (2008/06/13)
This invention relates to compounds of the formula: STR1 wherein R is an electron withdrawing group; R1 is H or COZ; X1 and X2 are independently H, lower alkyl, aryl, aryl lower-alkyl or polystyrene or R and X1 taken together with the carbon atoms to which they are attached form a ring containing from 4 to 15 ring carbon atoms and may contain up to 2 heteroatoms, wherein the heteroatoms are O, S, or N; and Z is an amino acid residue, a peptide residue or a leaving group. The compounds of the present invention are adaptable as blocking or protecting groups for an amine composition useful in peptide synthesis. The present invention is also directed to a method of protecting an amino group of an organic molecule during a reaction which modifies a portion of the molecule other than the protected amino group.
