[reaction: see text] The tethered aminohydroxylation (TA) of acyclic allylic carbamates has been achieved in a stereospecific and stereoselective manner. Unusually high levels of stereocontrol were observed in the oxidation of 1,1-disubstituted substrates.

Studies towards the biomimetic synthesis of mycaperoxide B (1) are described. We have established the synthesis of four diastereoisomers of mycaperoxide B methyl ester (1a) by employing a Michael addition across an α,β-unsaturated ester precursor 2 as the key step. This result strongly suggests stereocontrol in the addition of the hydroperoxide function-

Since Sharpless' discovery of the asymmetric aminohydroxylation (AA) reaction, a major challenge for chemists has been to find ways of controlling the regio- and stereochemical outcome of this important reaction. Detailed herein is a review of our novel approach towards gaining reliable and predictable regio- and stereocontrol through the use of a tethered carbamate to promote an intramolecular AA reaction, along with a description of the mechanism proposed for this new methodology.

[reaction: see text] Stereoselective aminohydroxylation and dihydroxylation using osmium(VIII) oxidants enabled the short and efficient synthesis of the aminocyclitol core of hygromycin A. In addition to allowing the selective introduction of the heteroatoms N and O, the use of osmium (via an osmate ester) as a protecting group for a 1,2-glycol is also reported. This tactic allowed efficient differentiation of otherwise equivalent hydroxyl groups and allowed us to complete the synthesis in short order (14 steps) and excellent overall yield (12%).

No abstract

Dedicated to Gerry Pattenden on the occasion of his 70 th birthday; an inspiring scientist and a genial companion.Abstract: Hydroperoxidation studies on a series of alkene substrates demonstrate the introduction of the hydroperoxide functional group into the required position for a biosynthetically inspired synthesis of mycaperoxide B.Mycaperoxide B (1) is a member of a group of eight structurally related terpene cyclic peroxides isolated from marine sponges of the genus Mycale. It was found to exhibit significant cytotoxicity against various cancer cell lines and antiviral activity. 1 The isolation of a hydroperoxidecontaining norsesterterpene endoperoxide from a marine sponge of the genus Sigmosceptrella has prompted Capon to propose a biosynthetic pathway for the synthesis of these norsesterterpene cyclic peroxides that invokes an intramolecular hydroperoxide Michael-type cyclisation. 2,3 Our synthetic planning to access the mycaperoxides has been inspired by Capon's proposal and is shown in Scheme 1. 3The proposed route would commence with the known decalone 5 and an organometallic species derived from 6. The key step in this sequence is the intramolecular Michael addition of the intermediate 2 to afford the cyclic peroxide that could be converted to the desired carboxylic acid 1.The work described in this communication, following previous investigations within our group, 4 is concerned with model studies of the Co(II)-catalysed peroxidation of alkenes related to the side chain of the putative hydroperoxidation substrate in order to validate this approach and establish the scope and limitations of the key hydroperoxidation step.The method chosen to introduce the hydroperoxide functionality utilises the methodology developed by Mukaiyama et al. 5 The catalyst Co(modp) 2 (modp = 1-morpholino-5,5-dimethyl-1,2,4-hexanetrione) was selected as the preferred catalyst for these reactions because of its reported high efficiency in the conversion of olefins into the corresponding triethylsilyl peroxide derivatives. 5-7

For Abstract see ChemInform Abstract in Full Text.

Efficient Acyclic Stereocontrol Using the Tethered Aminohydroxylation Reaction. -The title reaction displays excellent levels of syn stereoselectivity while providing complete control over the regio-and chemoselectivity of the oxidation. The 1,1-disubstituted systems show the highest level of stereocontrol. -(DONOHOE*, T. J.; JOHNSON, P. D.; PYE, R. J.; KEENAN, M.; Org. Lett. 6 (2004) 15, 2583-2585; Chem. Res. Lab., Dep. Chem., Univ. Oxford, Oxford OX1 3TA, UK; Eng.) -Steudel 46-123