Search

Chiral non-racemic α-substituted sulfoxides have been allowed to react with O-silylated ketene acetals in the presence of a catalytic amount of ZnI2 in THF to give chiral non-racemic α-siloxy sulfides in >99% ee. This is the highest enantioselectivity reported to date for the Pummerer reaction.

The principles of echo-shifting with a train of observations (PRESTO) magnetic resonance (MR) imaging technique employs an MR sequence that sensitively detects susceptibility changes in the brain. The effectiveness of PRESTO MR imaging was examined for distinguishing between cerebellopontine angle (CPA) schwannomas and meningiomas in 24 patients with CPA tumors, 12 with vestibular schwannomas, and 12 with meningiomas. Histopathological study of surgical specimens showed that 11 of the 12 schwannomas contained hemosiderin deposits and all had microhemorrhages. One meningioma contained hemosiderin deposits and two involved microhemorrhages. Abnormal vessel proliferation, and dilated and thrombosed vessels were observed in all schwannomas and in 4 meningiomas. In addition to MR imaging with all basic sequences, PRESTO MR imaging and computed tomography were performed. PRESTO imaging showed significantly more schwannomas (n = 12) than meningiomas (n = 2) exhibited intratumoral spotty signal voids which were isointense to air in the mastoid air cells (p < 0.001). These spotty signal voids were significantly associated with histopathologically demonstrated hemosiderin deposits (p < 0.001), microhemorrhages (p < 0.01), and abnormal vessels (p < 0.04). The visualization of spotty signal voids on PRESTO images is useful to distinguish schwannomas from meningiomas.

The hypervalent iodine oxidation of phenol derivatives bearing aminoquinones at the ortho (9) or meta positions (19) in 2,2,2-trifluoroethanol was investigated with the aim of preparing novel antitumor compounds. Azacarbocyclic spirodienone derivatives (13) or phenol derivatives containing the 2,3-dihydro-1H-azepine systems (17, 20) were selectively obtained by the reaction of these phenol derivatives and the hypervalent iodine reagent, phenyliodine(III) bis(trifluoroacetate). The application of this reaction to phenol derivatives bearing aminoquinones (10−12) is also described.

Chiral, non-racemic sulfoxides were reacted with thiols and BSA in the presence of a catalytic amount of TMSOTf in MeCN at rt overnight to give the corresponding chiral, non-racemic anti-thioacetals with high diastereoselectivity.

Isolated pulmonary Langerhans cell histiocytosis (LCH) in adults is known to regress spontaneously after smoking cessation alone, but little is known about whether this rationale could also apply in cases of multisystem pulmonary LCH. In particular, pediatric patients with multisystem LCH including involvement in "risk organs" such as lungs often benefit from systemic chemotherapy. Here, we present a 37-year-old man with spontaneous regression of pulmonary lesions in multisystem LCH, achieved solely by smoking reduction following local treatment of bone lesions.

Chiral non-racemic α-substituted sulfoxides have been allowed to react with O-silylated ketene acetals in the presence of a catalytic amount of ZnI2 in THF to give chiral non-racemic α-siloxy sulfides in >99% ee. This is the highest enantioselectivity reported to date for the Pummerer reaction.

Chiral, non-racemic sulfoxides were reacted with thiols and BSA in the presence of a catalytic amount of TMSOTf in MeCN at rt overnight to give the corresponding chiral, non-racemic anti-thioacetals with high diastereoselectivity.

Various types of syn- and anti-β-substituted sulfoxides 6b–e, g reacted with ketene tert-butyldimethylsilyl acetal 2 in the presence of a catalytic amount of zinc iodide in acetonitrile to give high yields of the corresponding α-siloxy sulfides 7b–e, g stereoselectively. Similarly, chiral, nonracemic sulfoxides 6a, f, h, i reacted with acetal 2 in acetonitrile to give the chiral, non-racemic α-siloxy sulfides 7a, f, h, i in high yields.

The hypervalent iodine oxidation of phenol derivatives bearing aminoquinones at the ortho (9) or meta positions (19) in 2,2,2-trifluoroethanol was investigated with the aim of preparing novel antitumor compounds. Azacarbocyclic spirodienone derivatives (13) or phenol derivatives containing the 2,3-dihydro-1H-azepine systems (17, 20) were selectively obtained by the reaction of these phenol derivatives and the hypervalent iodine reagent, phenyliodine(III) bis(trifluoroacetate). The application of this reaction to phenol derivatives bearing aminoquinones (10−12) is also described.

Treatment of chiral, non-racemic vinyl sulfoxides with O-silylated ketene acetal in the presence of a catalytic amount of zinc chloride in tetrahydrofuran resulted in an enantioselective Pummerer-type reaction, affording a considerable yield of the corresponding enantiomerically enriched methyl 4-siloxy-4-sulfenylbutyrate in 78-82% ee.

Various types of syn- and anti-β-substituted sulfoxides 6b-e, g reacted with ketene tert-butyldimethylsilyl acetal 2 in the presence of a catalytic amount of zinc iodide in acetonitrile to give high yields of the corresponding α-siloxy sulfides 7b-e, g stereoselectively. Similarly, chiral, nonracemic sulfoxides 6a, f, h, i reacted with acetal 2 in acetonitrile to give the chiral, non-racemic α-siloxy sulfides 7a, f, h, i in high yields.

The first highly asymmetric Pummerer-type cyclization of chiral, non-racemic β-amido sulfoxides to enantiomerically enriched β-lactams (80-85% ee) is described. S- and R-Sulfoxides (S-2a-d and R-2a-c) were treated with O-methyl-O-tert-butyldimethylsilyl ketene acetal 1 in the presence of a catalytic amount of zinc chloride in methylene dichloride to give predominantly the corresponding 4R- and 4S-β-lactams (R-3a-d and S-3a-c) in more than 80% ee. These results show that the stereoinduction is governed by the absolute configuration of the sulfoxides. Optically pure R- and S-3c were readily obtained by simple recrystallization in about 60% yield. The usefulness of the chiral, non-racemic 4-tolylsulfanyl-β-lactams 3a-d has been shown by their conversion into the key intermediate 11 for the optically pure carbapenem antibiotic, (+)-PS-5.

Treatment of chiral, non-racemic vinyl sulfoxides with O-silylated ketene acetal in the presence of a catalytic amount of zinc chloride in tetrahydrofuran resulted in an enantioselective Pummerer-type reaction, affording a considerable yield of the corresponding enantiomerically enriched methyl 4-siloxy-4-sulfenylbutyrate in 78-82% ee.

The Pummerer-type reaction of acyclic and rigid cyclic sulfoxides with ketene tert-butyldimethylsilyl methyl acetal 2 in the presence of a catalytic amount of zinc iodide in acetonitrile has been shown to proceed with highly stereoselective deprotonation of the α-methylene proton. A plausible reaction mechanism involving an anti elimination process is proposed based on an isotope labelling experiment using syn- and anti-[α-2H1]benzyl methyl and [α-2H1]benzyl tert-butyl sulfoxides.