Synthesis of the three stereoisomers of auxin‐glutaric acid to confirm the non‐existence of Kögl's auxin‐a and ‐b

Abstract

All of the three possible stereoisomers of (5S,l'S)-4-carboxy-5-methyl-1-(1'-methylpropy1)heptanoic acid were synthesized and their stereostructures assigned unambiguously by I3C-NMR and X-ray analyses. The melting points and the specific rotations of the three isomers were quite different from those reported for Kogl's auxin-glutaric acid and its two stereoisomers. This fact indicates the non-existence of Kogl's auxin-a and -b.

Structure-Elucidating Total Synthesis of the (Polyenoyl)tetramic Acid Militarinone C

“… a Reagents and conditions: (a) NEt 3 , propionic anhydride, CH 2 Cl 2 , 25 °C, 30 min, 92% (ref , 95%); (b) i Pr 2 NH, LiCl, n BuLi, THF, −78 to 0 °C, 5 min; ( S,S )- 18 , −78 °C, 1 h; 0 °C, 15 min; 25 °C, 5 min; EtI, 25 °C, 15 h; 94% (ref , 88%); (c) i Pr 2 NH, n BuLi, THF, −78 °C, 10 min; 0 °C, 10 min; BH 3 ·NH 3 , 0 °C, 15 min; 25 °C, 15 min; ( S,S,R )- 26 , 25 °C, 2 h; 76% (ref , 85%); (d) TsCl, pyridine, 0 °C, 12 h, 83% (ref , 99%); (e) NaI, DMF, 60 °C, 1.5 h, 58% (ref , 89%); (f) i Pr 2 NH, LiCl, n BuLi, THF, −78 to 0 °C, 5 min; ( S , S )- 18 , −78 °C, 1 h; 0 °C, 15 min; 25 °C, 5 min; ( R )- 28 , 25 °C, 24 h; 88% (ref for the enantiomer, 94%; ref , 95%); (g) i Pr 2 NH, n BuLi, THF, −78 °C, 10 min; 0 °C, 10 min; BH 3 ·NH 3 , 0 °C, 15 min; 25 °C, 15 min; ( S,S,R , R )- 15 , 25 °C, 2 h; 74% (ref , 88%); (h) NMO, 4 Å molecular sieves, CH 2 Cl 2 , 25 °C, 15 min; TPAP (5 mol %), 25 °C, 1 h; 77% (ref , 98%); (i) (COCl) 2 , DMSO, THF, −78 °C, 2 min; 0 °C, 3 min; alcohol ( R,R )- 29 , −78 °C, 2 min; 0 °C, 15 min; NEt 3 , 0 to 25 °C; 76%. TPAP = Pr 4 NRuO 4 . …”

“…Our route to western building block (S)-8 began with three known steps (Scheme 2): trans-hydrobromination of propiolic The stereogenic C−CH 3 bonds of eastern building block (R,R)-9 were established by asymmetric Myers alkylations 23 of the Li enolate of the amide (S,S)-18, prepared from pseudoephedrin [(S,S)-26] and propionic anhydride 23 (Scheme 3). Ethylation of its enolate 24 [→94% (S,S,R)-26], reduction with LiBH 2 •NH 3 23 [→76% alcohol (R)-19 24 ], tosylation [→ 83% (R)-27 25 ], and a Finkelstein reaction [→58% (R)-28 26 ] provided an iodide of 99% ee. It was combined with another equivalent of the Li enolate of the amide (S,S)-18 to amide (S,S,R,R)-15 24,27 (88% yield).…”

Iridoids from the Rhizomes and Roots of Valeriana jatamansi

“…These data revealed the presence of an acetate group at C-11. A TOCSY experiment showed correlations among the C-2−C-6 protons of a β-Me-isovalerate function, at δ 2.26 (2H, m), 2.11 (1H, m), 1.24 (2H, m), 0.94 (3H, t, J = 6.0 Hz), and 1.08 (3H, d, J = 6.1 Hz), demonstrating that they belong to the same spin system. The C-2 protons of the β-Me-isovalerate group showed a long-range 13 C− 1 H correlation with a carbonyl carbon at δ 170.4, whereas the carbonyl carbon showed a three-bond correlation with H-1 ( δ 5.98) in the HMBC spectrum.…”

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

“…These are versatile intermediates, which can also be transformed into other useful derivatives by making use of the chemistry of the dithioketal moiety. As an illustrative example, ultrasound-assisted Ra-Ni-mediated desulfuration of 218 (R = Et and 2-naphthyl) was effected to afford known malonates 219 (R = Et [111] and 2-naphthyl [112] ) in 75 and 71 % yield, respectively. As the overall result, hydrazone 51e was used as a chiral reagent for the asymmetric nucleophilic methylation of alkylidenemalonates with the racemization-free direct dithioketalation as the key step in this process.…”