Synthetic approach towards tetrodotoxin. I. Diels-Alder reaction of α-oximinoethylbenzoquinones with butadiene

Recent Advances in Substrate-Controlled Asymmetric Induction Derived from Chiral Pool α-Amino Acids for Natural Product Synthesis

“…Cycloaddition reactions have also been adapted for the proline-derived total synthesis of natural products. Sarpong et al completed the impressive syntheses of ent-citrinalin B (15) and cyclopiamine B (16) as shown in Scheme 3 [13][14][15]. The authors utilized the chirality of D-proline for the stereoselective construction of a cis-fused ring system within final products 15 and 16.…”

“…Unsaturated cyanoamide 12 was prepared from D-proline in 55% yield over seven steps for use as a dienophile in the key face-selective Diels-Alder reaction. When diene 13 underwent cycloaddition with 12 in the presence of Lewis acid [16], desired product 14 was obtained in 73% yield after a basic work-up. As dienophile 12 provided a convex face environment in the bicyclic ring system, diene 13 approached the β-face of the unsaturated lactam ring selectively, establishing the two adjacent stereocenters in tricyclic ketone 14 simultaneously.…”

“…As dienophile 12 provided a convex face environment in the bicyclic ring system, diene 13 approached the β-face of the unsaturated lactam ring selectively, establishing the two adjacent stereocenters in tricyclic ketone 14 simultaneously. Subsequent steps transformed 14 into ent-citrinalin B (15) and cyclopiamine B (16). Another substrate-controlled chiral induction application of L-proline is summarized in Scheme 2.…”

Modern Methods for Total Synthesis of Important Oxindole Alkaloids

“…This served as a substrate for an unprecedented formal cycloisomerization that probably proceeds via a metal vinylidene intermediate, 35 anti-Markovnikov hydration, and Knoevenagel condensation to give tetrahydroindolizinone 230. At this stage, a SnCl 4 -catalyzed Diels-Alder reaction between 230 and diene 231, 36 and a subsequent basic workup, afforded an enone (not shown), which was iodinated to yield iodoenone 232 (Scheme 42). 37 The hydrolysis of the nitrile group of 232 was achieved using a Pt-complex 233 to afford the corresponding carboxamide, 38 which served as a substrate for a Hofmann rearrangement that was effected with phenyliodosyl bistrifluoroacetate to yield carbamate 234.…”

Synthese des all-cis-Perhydronaphtho[1,8-bc]furansystems durch Photocyclisierung

“…: 217-220 °C; IR (cm-1): 3386 (br), 2950, 2892, 2845, 1707, 16101H-NMR (CDCI3, c5): 1.67 (d, mit D20 austauschbar, 1H, JOH,6 = 3.1, OH), 2.10 (m,2H,2.30 (ddd,1H,J4,4 = 18.2,J4 .... 5endo = 1.9,J4 .... sexo = 8.6,2.45 (ddd,1H,J4,4 = 18.2,J4e,eo,Se,ao = 8,J4e,ao,sexo = 11,ao),3.23 (dd,1H,J7.2 = 11.6,J7,6 =3.4,, 3.46 (d,1H,Je.v = 11.6,3.56 (s,3H,OCH3),3.61 (s,3H,OCH3) ,4.45 (m,1H,J6,7 = 3.4,J6,OH = 3.1,), 129.1 (C-10 (9)), 113.7 (C-11), 76.3 (C-1 (8)), 74.8 (C-8 (1)), 62.2 (C-6), 56.6 (C-2 (7)), 55.0 (C-7 (2) 5,0.5,0.3,0.2,M+),339/341/343 (88.5,90.8,30.5,…”