Palladium-catalyzed sulfinylzincation: 1-alkynyl sulfoxides as a sulfinyl anion equivalent.

[reaction--see text] Novel Pd-catalyzed sulfinylzincation of activated alkynes was developed, wherein 1-alkynyl sulfoxides work as a sulfinylating agent. Transfer of the sulfinyl group proceeded in a highly syn-selective fashion, giving a beta-sulfinyl vinylzinc species. Using 3,3-dimethyl-1-butynyl p-tolyl sulfoxide as a sulfinyl source, heterocoupling with propiolate derivatives was also accomplished.

Total synthesis of (+/-)-scopadulin.

The first total synthesis of (+/-)-scopadulin, an aphidicolane diterpene, is described. The core structure (A/B/C/D ring system) was constructed by an initial synthesis of the B/C/D ring system by our reported methods and a subsequent A ring cyclization by intramolecular aldol condensation. A highly stereoselective cyanation of the tetracyclic enone by Et2AlCN gave a trans-fused A/B ring system with a beta-cyanide at C-4. Stereoselective construction of a quaternary carbon at C-4 was achieved by alpha-alkylation of the cyano group and conversion of the sterically hindered cyano group to a methyl group via our novel reaction for conversion of primary aliphatic amines into alcohols. Finally, the total synthesis of (+/-)-scopadulin was accomplished by a highly chemo- and stereoselective methylation at C-16 and modification of the C-4 alpha-functionality. The stereoselectivity observed in the MeTi(O-i-Pr)3-mediated methylation for the generation of a tertiary axial alcohol at C-16 is extremely high.

Highly stereoselective intramolecular Michael addition using alpha-sulfinyl vinyllithium as an unprecedented Michael donor.

[figure: see text] The first example of an asymmetric intramolecular Michael addition reaction using alpha-lithiated vinylic sulfoxide as a Michael donor is reported. Michael addition of the alpha-lithiated vinylic sulfoxide to (Z)-enoates proceeds with high diastereoselectivity to give the adducts having a stereogenic center with (R)-configuration at the beta-position of the ester in the cyclopentene ring formation. The selectivity was reversed in the six-membered ring formation. On the other hand, the corresponding (E)-enoates provided Michael adducts with poor diastereoselectivity.

First total synthesis of mosin B.

[figure: see text] The first total synthesis of mosin B and a diastereomer was accomplished using asymmetric desymmetrization of the sigma-symmetric diol and the Nozaki-Hiyama-Kishi reaction as the key steps. The THF core segment was stereoselectively constructed employing a stereodivergent synthesis starting from a common intermediate, 4-cyclohexene-1,2-diol, based on a desymmetrization strategy. By virtue of these synthetic results, it is suggested that the absolute configuration is 1a.

The first total synthesis of (+/-)-scopadulin, an antiviral aphidicolane diterpene.

[reaction: see text] The first total synthesis of (+/-)-scopadulin was accomplished by a stereoselective construction of a quaternary carbon at C-4, conversion of the hindered cyano group to a methyl group via our novel reaction for conversion of primary aliphatic amines into alcohols, and a highly chemo- and stereoselective methylation at C-16.

Efficient one-step conversion of primary aliphatic amines into primary alcohols: application to a model study for the total synthesis of (+/-)-scopadulin.

[reaction: see text] Treatment of primary aliphatic amines with KOH in diethylene glycol at 210 degrees C gives primary alcohols directly in good yields. A synthetic application to a model study of (+/-)-scopadulin is also described.

C(2)-Symmetric bis-sulfoxide: A novel chiral auxiliary for asymmetric desymmetrization of cyclic meso-1,2-diols

A new heterocyclic compound, C(2)-symmetric bis-sulfoxide 1, has been found to be an efficient chiral auxiliary for asymmetric desymmetrization of cyclic meso-1,2-diols via diastereoselective acetal fission. Both (R,R)- and (S,S)-1 are readily synthesized with high optical purity via asymmetric oxidation of 1, 5-benzodithiepan-3-one (2). After acetalization of meso-1,2-diols 6a-e and a mono-TMS ether 6f with this chiral auxiliary 1, the resulting acetals 7a-f were subjected to base-promoted acetal fission upon treatment with potassium hexamethyldisilazide (KHMDS) followed by acetylation or benzylation to give the desymmetrized diol derivatives 8a-f with high diastereoselectivity. The chiral auxiliary 1 is readily removed by acid-promoted hydrolysis and can be recovered without a loss in enantiomeric excess.