Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• ; Introduction The aminal system (N,N-acetal) is the structurally equivalent analogue of the O,O-acetal. In the literature this moiety is found as a core element in various important structures, for example in the naturally occurring alkaloids tetraponerine T1 to T8 from the venom of the New Guinean ant

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• [33][34], led to an unwanted cleavage of the silyl ether and furnished a mixture of the desired product 8, the TBDMS cleavage product 9 and the corresponding O,O-acetal 10 (Table 1, entry 1). Hence, further reaction conditions using different acid catalysts and solvents were investigated. Changing the

• catalyst to pyridinium p-toluenesulfonate (PPTS) only led to small amounts of the product after prolonged reaction times and could not suppress the formation of the O,O-acetal (Table 1, entries 2 and 3). The use of racemic camphorsulfonic acid (CSA) in toluene and acetone, respectively, resulted in the

• , followed by concomitant acidic cleavage of the N,O- and O,O-acetal protecting groups leading to building block 22 in 89% yield (Scheme 3). Aldehyde 22 can be used for the connection of the (2S,3S)-3-hydroxyleucine motif of C-series muraymycins (such as muraymycin C1 (1c), Figure 1) to the nucleoside moiety

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• a Brønsted acid. Keywords: allylation; hemiacetal; O,O-acetal; O,S-thioacetal; peroxyacetal; Re2O7; S,S-acetal; Introduction The synthetically important conversions of hemiacetals to acetals, thioacetals, or homoallyl ethers are typically achieved through activation of the substrate with a strong