Introducing Oxo-Phenylacetyl (OPAc) as a Protecting Group for Carbohydrates

Abstract

A series of oxo-phenylacetyl (OPAc)-protected saccharides, with divergent base sensitivity profiles against benzoyl (Bz) and acetyl (Ac) were synthesized, and KHSO5/AcCl in methanol was identified as an easy, mild, selective, and efficient deprotecting reagent for their removal in the perspective of carbohydrate synthesis. Timely monitoring of AcCl reagent was supportive in both sequential and simultaneous deprotecting of OPAc, Bz, and Ac. The salient feature of our method is the orthogonal stability against different groups, its ease to generate different valuable acceptors using designed monosaccharides, and use of OPAc as a glycosyl donar.

Epoc group: transformable protecting group with gold(iii)-catalyzed fluorene formation

“…Because of the requirement for synthesizing complex molecules and constructing efficient synthetic strategies, the novel orthogonal protecting groups have still been developed recently such as reduction-labile, tetrazine-labile and Cu(I)-labile protecting groups. [31][32][33][34] This work provided the novel orthogonality in the series of protecting groups as a gold(III)labile protecting group with the extremely mild conditions for its removal. Its applicability to SPPS enables the efficient synthesis of branched and cyclic peptides including complex natural products, which require multiple orthogonal protecting groups.…”

Advances in Protecting Groups for Oligosaccharide Synthesis

“…Another study of the protecting group directly related to the stereochemical outcome of glycosylation is picoloyl (Pico) protecting group . When this protecting group is placed at the 6‐position of d ‐glucoside, high selectivity of 1,2‐ trans product is observed.…”

“…Another study of the protecting group directly relatedt o the stereochemical outcome of glycosylationi sp icoloyl (Pico) protecting group. [12,27] When this protecting group is placed at the 6-position of d-glucoside, high selectivity of 1,2-trans product is observed. Conversely, when the same group is positioned att he equatorially oriented 4-OHo ft he d-glucosyl donor, substrate selectivity of the glycosylation was reversed.…”

“…Recently, Vishwakarma and co‐workers introduced oxo‐phenylacetyl(OPAc) protecting group as an ester type group which can be removed in the presence of Ac and Bz under mildly basic conditions …”

Cyanomethyl (CNMe) ether: an orthogonal protecting group for saccharides

“…Following the success of pivaloyl (Piv) and levulinoyl (lev) protection of hydroxyls, diverse ester based PGs that allow reagent-controlled deprotection have been reported. [9][10][11][12][13][14] In spite of their widespread application in multi-step organic synthesis, the "disarming" nature of ester groups has frequently made them less favorable in comparison to the "arming" ether based PGs in oligosaccharide synthesis. 15 Since benzyl ethers (OBn) are generally considered as permanent PGs requiring harsh reaction conditions for their removal with low site selectivity among the different sugar hydroxyls, substituted benzyl ethers that can be handled under milder conditions have found extensive synthetic application.…”