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1.
[structure: see text] A convergent, stereoselective assembly of the C1-C21 (C1'-C21') fragment of SCH 351448, a 28-membered bis-lactone natural product, has been developed. A highly efficient approach to this fragment assembles 75% of the carbon skeleton and all the stereochemical elements present in the natural product. In addition, an interesting boron ligand effect on the diastereoselectivity of a key aldol reaction with methyl ketone-derived enolborinates is reported. 相似文献
2.
A convergent synthesis of the C(18)-C(34) fragment of amphidinolide C and the C(18)-C(29) fragment of amphidinolide F is reported. The approach involves the synthesis of the common intermediate tetrahydrofuranyl-β-ketophosphonate via cross metathesis, Pd(0)-catalyzed cyclization, and hydroboration-oxidation. The β-ketophosphonate was coupled to three side chain aldehydes using a Horner-Wadsworth-Emmons (HWE) olefination reaction to give dienones, which were reduced with l-selectride to give the fragments of amphidinolide C and F. 相似文献
3.
[formula: see text] A C(1)-C(14)-containing fragment of callipeltoside A (1, Scheme 1) was synthesized efficiently via a dianion aldol coupling reaction between aldehyde 2 and ketoester 3. A surprising lack of reactivity between the alkenes in 13 and the Grubbs initiator 15 was encountered. An equally surprising rate acceleration of the reaction between 15 and allylic alcohols (alk-1-en-3-ols) as well as their subsequent cleavage to methyl ketones was discovered. In situ 1H NMR analysis has proven to be a very useful tool for monitoring RCM reactions of complex substrates such as 13. 相似文献
4.
[reaction: see text] The C1-C9 fragment of callipeltoside (17) was prepared in 12 steps and 7.2% overall yield from bicyclic lactone (+)-4. Key steps include a stereoselective epoxidation and further regiocontrolled nucleophilic opening of the oxirane ring to install two vicinal stereocenters (C5 and C6), and the use of bis(trimethylsilyl) peroxide and a catalytic amount of Sn(IV) chloride for the chemoselective Baeyer-Villiger oxidation of unsaturated cyclopentanone 15. 相似文献
5.
The synthesis of the C1-C16 framework of the ajudazols has been achieved taking advantage of a highly selective isobenzofuran oxidative rearrangement and a key Stille coupling to introduce the key C14-C15 bond. 相似文献
6.
Efficient syntheses of suitably functionalized top and bottom fragments of tetrafibricin are described. The bottom fragment is prepared by two consecutive Kocienski-Julia couplings, while the top fragment synthesis features a dithiane alkylation and a Horner-Wadsworth-Emmons reaction. 相似文献
7.
A synthesis of the C1-C12 fragment of amphidinolide T1 utilising Evans’ aldol, oxy-Michael and cross metathesis reactions as the key steps is described. 相似文献
8.
[reaction: see text] A synthesis of the C(43)-C(67) fragment of amphidinol 3 (AM3) has been accomplished by a route that features the use of a double allylboration reaction for synthesis of 1,5-diol 4b, which serves as a precursor to dihydropyran 11. 相似文献
9.
Stereoselective syntheses of the C(1)-C(9) fragments 18 and 28 of amphidinolide C have been developed. The first-generation sequence involves a diastereoselective chelate-controlled [3 + 2]-annulation reaction of 6 and 7, while the second-generation synthesis involves an intramolecular hetero-Michael cyclization of 8. 相似文献
10.
Synthesis of the C1-C23 fragment in spirastrellolide A is described, featuring a cyclic acetal-tethered RCM for stereoselective constructions of spiroketal, and a 1,3- anti aldol involving methyl ketone enolate and Mukaiyama conditions. 相似文献
11.
Jia Liu 《Tetrahedron letters》2006,47(34):6121-6123
Synthesis of the C1-C16 fragment of spirastrellolide A is described here featuring Sharpless asymmetric epoxidation, an acid promoted O-1,4-addition, and Mukaiyama 1,3-anti-aldol. 相似文献
12.
[reaction: see text] The synthesis of the C1-C13 fragment 3 of leucascandrolide A has been completed utilizing a stereoselective and regioselective reductive cleavage of a highly functionalized spiroketal to incorporate the cis-2,6-disubstituted tetrahydropyan. The spiroketal was constructed by addition of a lithiated pyrone 5 to aldehyde 6. 相似文献
13.
The synthesis of C1-C20 and C15-C27 segments of Aplyronine A is described. Oxidative cleavage of cyclic vinyl sulfones has been used to prepare key fragments of Aplyronine A. Key precursors are united by Horner-Wadsworth-Emmons and Julia-Kociensky olefination for the respective elaboration of the C1-C20 and C15-C27 segments. 相似文献
14.
[reaction: see text] The key fragment (2a or 2b) in a total synthesis of the cytotoxic macrolide (-)-amphidinolide K (1) has been achieved from synthons C9-C14 (3) and C15-C22 (4), which have both been prepared from glutamic acid in good overall yields. 相似文献
15.
Handa M Scheidt KA Bossart M Zheng N Roush WR 《The Journal of organic chemistry》2008,73(3):1031-1035
A synthesis of the C(1)-C(11) fragment of apoptolidin A has been accomplished by a convergent route involving the stereoselective glycosidation of 9 and the Suzuki cross-coupling reaction of bromodienoate 7 and the vinylborane generated via chemoselective hydroboration of diyne 6 with diisopinocampheylborane. 相似文献
16.
[reaction: see text] A stereoselective synthesis of the C(1)-C(19) fragment of tetrafibricin has been accomplished via a highly diastereoselective double allylboration reaction of 6-8 and an iodonium ion promoted urethane cyclization for the installation of the C(15) alkoxy function in 3. 相似文献
17.
A. F. Sviridov V. S. Borodkin M. S. Ermolenko D. V. Yashunskii 《Russian Chemical Bulletin》1989,38(3):600-606
Conclusions A synthesis of a C5-C9-fragment common to erythronolides A and B was carried out starting from levoglucosan.For previous communications, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 674–680, March, 1989. 相似文献
18.
A highly stereoselective synthesis of the C(1)-C(11) fragment 4 of peloruside A has been accomplished via a stereoselective double allylboration and an intramolecular epoxide opening to provide the functionally dense C(3)-C(11) segment 14. A glycolate aldol reaction was then employed to introduce the remaining stereocenters at C(2)-C(3). [reaction: see text] 相似文献
19.
Roberta A. Oliveira Luis H.S. Rahmeier Joao V. Comasseto Paulo H. Menezes 《Tetrahedron letters》2008,49(40):5759-5761
An enantioselective and convergent synthesis of the C7-C24 fragment of Macrolactin F was achieved from four main fragments. A hydrotelluration/transmetalation sequence was used to install the E,Z diene present in the molecule, while a hydrozirconation/transmetalation sequence was used to connect two advanced intermediates. 相似文献
20.
Matthew Ball 《Tetrahedron letters》2004,45(47):8737-8740
A synthesis of the C(1)-C(16) fragment of the brysostatins has been developed. Key steps are the stereoselective copper(I) catalysed addition of allylmagnesium bromide to an alkynyl ester, a condensation of a βγ-unsaturated aldehyde with a ketophosphonate, and the formation of the B-ring under mild conditions by stereoselective intramolecular conjugate addition. 相似文献