Stereoselective synthesis towards (+)-trans-kumausyne employing vinylogous Mukaiyama type reaction on an α-chloro sulfide

1199-1205A stereoselective synthesis towards (+)-trans-kumausyne is disclosed. The key steps of the synthesis include stereoselective C-C formation employing vinylogous Mukaiyama type reaction of an α-chloro sulfide with 2-trimethylsiloxy furan and base-catalyzed isomerization followed by intramolecular oxa-Michael reaction

Stereoselective preparation of a key intermediate toward the synthesis of nelfinavir

821-828A stereoselective synthesis of an intermediate that can be elaborated into the potent HIV-protease inhibitor, nelfinavir, is described. The key step of the reaction sequence is the stereoselective preparation of a bromosulfonamide from an olefin using the sulfilimine moiety as an intramolecular nucleophile

Approaches to the stereoselective synthesis of (+)-lactacystin utilizing organocatalytic reactions

1075-1085Efforts toward a stereoselective synthetic route to (+)-lactacystin based on organocatalytic transformations and intramolecular amino hydroxylation for creating the tetrasubstituted stereogenic center are described. Tethered aminohydroxylation of an allylic carbamate following Donohue's protocol affords a regioisomeric amino alcohol derivative, while Lewis acid promoted epoxide opening by a trichloroacetimidate yields a tetrahydrofuran derivative

Stereoselective synthesis towards (+)-trans-kumausyne employing vinylogous Mukaiyama type reaction on an α-chloro sulfide

A stereoselective synthesis towards (+)-trans-kumausyne is disclosed. The key steps of the synthesis include stereoselective C-C formation employing vinylogous Mukaiyama type reaction of an α-chloro sulfide with 2-trimethylsiloxy furan and base-catalyzed isomerization followed by intramolecular oxa-Michael reaction

Toward a stereoselective synthesis of tetrahydroxy long chain base (LCB) and the synthesis of analogs of mannostatin A

559-579Efforts toward the stereoselective synthesis of tetrahydroxy long chain base and analogs of mannostatin A are described. The sulfinyl moiety has been efficiently utilized as an intramolecular nucleophile for oxidative functionalization of an alkene and regioselective opening of an epoxide. Nucleophilic addition to sulfinylimine has been used for the introduction of amino stereogenic center. Pummerer reaction has not been successful with a free N-H group at -carbon. Pummerer reaction on a N,O-acetonide furnishes an aldehyde. Attempted Wittig olefination to access the protected derivative of long chain base have failed. The analog of mannostatin could not be prepared by intramolecular addition of a sulfinyl carbanion to an imine but could be prepared by radical chemistry

Synthesis based on cyclohexadienes: Part 10 synthesis of 5,5-dimethyl-7-methoxy-4-oxatricyclo[4.3.1.0]decan-2-ones

Synthesis of 5, 5-dimethyl- 7-methoxy-4 -oxatricyclo[4,3,1,0(3,7)]- decan-2-one 3a, a novel heterocyclic ring system present in morellin 1, and its 3-substituted derivatives 3b-e, is described from the Diels-Alder adducts 7, available from 1-methoxycyclohexa-1,4-dienes 4. Two routes, which involved the halocyclisation and the oxidative addition, were investigated for the conversion of the adducts 7 into 3. While the halocyclisation method resulted in mixtures, excellent yields of the target molecule were obtained by the second method. Solvolysis of the bromoether 9 resulted in a mixture of rearranged products 10, 13, 15 and 16

Synthetic studies on morellin. Part 4: Synthesis of 2,2-dimethyl- 12-[3-methylbut-2-enyl]-2H,6H-pyrano[3,2-b]xanthen-6-one

A new synthesis of 2,2-dimethyl-12-[3-methylbut-2-enyl]-2H,6H-pyrano[3,2-b]xanthen-6-one (7) is described from 1,3-dihydroxyxanthone and involved the preparation of a linear dihydropyranoxanthone (26), its conversion into the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7)

Synthesis of 5,5-Dimethyl-7-methoxy 4-oxatricyclo [4,3,1,03,7]decan-2-ones

Two new synthetic routes for the preparation of the title compound and its 3-substituted derivatives, a novel ring system present in morellin and other related natural products, are reported from the readily available dihydroanisoles