Total synthesis of calicheamicin .gamma.1I. 2. Development of an enantioselective route to (-)-calicheamicinone

The Synthesis and Crystal Structure of a Novel Pesticide Intermediates

“…1. In our paper, 2,3-dimethylaniline was used as materials, 3-(6-bromo-2-methyl-3-methylsulfonylphenyl)-4,5-dihydro-1,2-oxazole was synthesized through diazotization reaction [13], electrophilic bromination reaction [14,15], oxidation reaction [16], radical bromination reaction, oxidation reaction [17], condensation reaction and 1,3-dipolar cycloaddition reaction [18][19][20][21][22].…”

B-Methoxydiisopinocampheylborane (Ipc2BOMe): A Pinene Based Auxiliary for Asymmetric C-C Bond-Forming Reactions

“…Simple treatment of alkoxyallyl lithium with Ipc 2 BOMe and BF 3 ·Et 2 O provides [(Z)-γ-alkoxyallyl]diisopinocampheylborane (Table 1, entry 3) that gives rise to syn-diols (Scheme 5, FG = MeO, MEMO). In natural product synthesis, this transformation has found numerous applications, and the antibiotics calicheamycin γ ' 1 [19] and herbimycin A, a herbicidal, antiviral and antitumor active metabolite of a Streptomyces strain, were first synthesized using [(Z)-γ-alkoxyallyl]diisopinocampheylborane in key steps [20]. The stereoselective alkoxyallylboration of amino compounds like 18 opens a versatile route to polyhydroxylated alkaloids, for example castanospermine and swainsonine [16,21], both known as potent glucosidase inhibitors, and analogues such Scheme 6 Preparation of functionalized allylation reagents Configurationally labile aldehydes may be allylated in situ, following low temperature reduction of esters, such as 25, and lactones with DIBAL-H and subsequent trapping of the ensuing aldehyde with the allylation reagent [30].…”

Asymmetric synthesis of methyl 6-deoxy-3-O-methyl-α-l-mannopyranoside from a non-carbohydrate precursor

“…5 Methyl 6-deoxy-3-O-methyl-a-L Lmannopyranoside (1), is a subunit of the antitumor antibiotic calicheamicin c I 1 . 6,7 Various methods for synthesis of 6-deoxy-L L-mannose have been developed, [7][8][9] but all have started with preformed sugars. For example, Halcomb et al reported the synthesis of dimethylsilyl-3-O-methyl-a-L L-mannopyranose from a preformed sugar, 3,4-di-O-acetyl-6-deoxy-L L-glucal.…”