Total synthesis of the proposed structure of iriomoteolide-1a
摘要:
Full details of the total synthesis of the proposed structure of iriomoteolide-1a (1) are described. The key steps include (i) a Sakurai reaction between allylsilane 11 and aldehyde 10 that bears both a tertiary chiral center and vinyl iodide moiety (ii) an anti-aldol reaction to construct the C18/C19 chiral centers (iii) a B-alkyl Suzuki-Miyaura coupling reaction to assemble the C7-C23 fragment, and (iv) a macrocyclic ring-closing metathesis to complete the construction of the target molecule. Two different approaches to access penultimate precursor 2 are delineated. The NMR spectra of the synthetic iriomoteolide-1a (1) were found not to match those reported for the natural product bringing into question its true structural identity. (C) 2011 Elsevier Ltd. All rights reserved.
Total synthesis of the proposed structure of iriomoteolide-1a
摘要:
Full details of the total synthesis of the proposed structure of iriomoteolide-1a (1) are described. The key steps include (i) a Sakurai reaction between allylsilane 11 and aldehyde 10 that bears both a tertiary chiral center and vinyl iodide moiety (ii) an anti-aldol reaction to construct the C18/C19 chiral centers (iii) a B-alkyl Suzuki-Miyaura coupling reaction to assemble the C7-C23 fragment, and (iv) a macrocyclic ring-closing metathesis to complete the construction of the target molecule. Two different approaches to access penultimate precursor 2 are delineated. The NMR spectra of the synthetic iriomoteolide-1a (1) were found not to match those reported for the natural product bringing into question its true structural identity. (C) 2011 Elsevier Ltd. All rights reserved.
Synthetic studies toward bryostatin 1: preparation of a C1–C16 fragment by pyran annulation
作者:Gary E. Keck、Dennie S. Welch、Yam B. Poudel
DOI:10.1016/j.tetlet.2006.09.094
日期:2006.11
An expeditious assembly of a C(1)-C(16) subunit of bryostatin 1 is described. A pyran annulation reaction was utilized to form the B-ring by reaction of a hydroxy-allylsilane with a fully elaborated A-ring subunit. This annulation process proceeded with complete diastereoselectivity and in excellent isolated yield despite the presence of potentially sensitive functionality in the A-ring segment.
[structure:see text] The marinenaturalproduct hennoxazole A was synthesized by a convergent approach. The diastereoselective Mukaiyama aldol reaction with beta-alkoxy aldehyde was used to construct the tetrahydropyran segment, and the preparation of the nonconjugated triene moiety was accomplished via S(N)2 displacement of allylic bromide with vinyllithium and Takai's iodoolefination followed by
Synthetic Studies toward the Bryostatins: A Substrate-Controlled Approach to the A-Ring
作者:Gary E. Keck、Dennie S. Welch、Paige K. Vivian
DOI:10.1021/ol061173h
日期:2006.8.1
The synthesis of a C-1 - C-13 A-ring subunit of bryostatin 1 is detailed. The key features of the approach include the convergent fragment assembly with a highly stereoselective construction of the C-7-C-8 bond indicated above.
The antiviral marine natural product (-)-hennoxazole A was efficiently synthesized by a convergent approach. The stereoselective synthesis of the functionalized tetrahydropyran fragment was accomplished by the Mukaiyama aldol reaction, chelation-controlled 1,3-syn reduction, Wacker oxidation, and acid catalyzed intramolecular ketalization. The nonconjugated triene fragment was synthesized by S(N)2 displacement of an allylic bromide with vinyllithium and the CrCl2-mediated iodoolefination followed by palladium-catalyzed cross coupling with MeMgBr. The final steps include the fragment coupling using DEPC and oxazole synthesis via an oxidation/cyclodehydration process. (C) 2001 Elsevier Science Ltd. All rights reserved.