1. Monoselective o-C-H Functionalizations of Mandelic Acid and α-Phenylglycine
Navid Dastbaravardeh, Tetsuya Toba, Marcus E Farmer, Jin-Quan Yu J Am Chem Soc. 2015 Aug 12;137(31):9877-84. doi: 10.1021/jacs.5b04324. Epub 2015 Jul 30.
Pd-catalyzed C-H functionalization of mandelic acid and α-phenylglycine is reported. We have developed different protocols for the arylation, iodination, acetoxylation, and olefination of these substrates based on two different (Pd(II)/Pd(IV) and Pd(II)/Pd(0)) catalytic cycles. Four crucial features of these protocols are advantageous for practical applications. First, the α-hydroxyl and amino groups are protected with simple protecting groups such as acetates (Ac, Piv) and carbamates (Boc, Fmoc), respectively. Second, these protocols do not involve installation and removal of a directing group. Third, monoselectivity is accomplished. Fourth, no epimerization occurs at the vulnerable α-chiral centers.
2. 2-[(tert-But-oxy-carbonyl-amino)-oxy]acetic acid
Jing-Yu Zhang, Yan Tong, Shengqi Wang Acta Crystallogr Sect E Struct Rep Online. 2011 Sep 1;67(Pt 9):o2324. doi: 10.1107/S1600536811031990. Epub 2011 Aug 11.
The title compound, C(7)H(13)NO(5), was prepared by the condensation of O-(carb-oxy-meth-yl)hydroxyl-amine and (Boc)(2)O (Boc = but-oxy-carbon-yl).In the crystal, mol-ecules are linked by weak inter-molecular N-H⋯O hydrogen bonds.
3. C11 /C9 Helical Folding in αβ Hybrid Peptides Containing 1-Amino-cyclohexane acetic acid (β3, 3 -Ac6 c)
Naiem Ahmad Wani, Srinivasarao Raghothama, Umesh Prasad Singh, Rajkishor Rai Chemistry. 2017 Jun 22;23(35):8364-8370. doi: 10.1002/chem.201700265. Epub 2017 May 30.
The present study describes the solid-state conformation of αβ hybrid peptides, Boc-Leu-β3, 3 -Ac6 c-OH, P1; Boc-Leu-β3, 3 -Ac6 c-Leu-β3, 3 -Ac6 c-OMe, P2; and Boc-Leu-β3, 3 -Ac6 c-Leu-β3, 3 -Ac6 c-Leu-OMe, P3. The dipeptide P1 adopts extended conformations, whereas tetrapeptide P2 and pentapeptide P3 favor a helical conformation stabilized by mixed types of C11 /C9 intramolecular hydrogen bonds. In peptide P3, the amino group of β3, 3 -Ac6 c(2) and β3, 3 -Ac6 c(4) residues occupies axial orientation, whereas in P2 it occupies axial and equatorial orientations for residues β3, 3 -Ac6 c(2) and β3, 3 -Ac6 c(4), respectively. The self-assembly of P3 forms channels filled with solvent molecules that present interesting patterns.
