* Osram now sees FY adj EBITDA at 640 mln euros
* Previously saw core profit of 700 mln
* Says accelerating shift to high-tech focus
* Shares drop 11 percent (Recasts, adds share price, analyst comments)
FRANKFURT, April 25 (Reuters) - Shares in German lighting group Osram dropped to a 15-month low on Wednesday after the group cut its 2018 core profit guidance due to "muted" business in the first half of the year and a weak dollar versus the euro.
Osram, which struggled to win over investors to an ambitious Asian expansion plan, said it would accelerate its move to focus on fast-growing high-tech markets while negotiating with German labour representatives over a reorganisation.
The Munich-based company said it now expected full-year adjusted earnings before interest, taxes, depreciation and amortisation (EBITDA) of 640 million euros ($782 million), below a previous target of about 700 million for its fiscal year to end-September and a year-earlier figure of 695 million.
Shares in Osram were down 11 percent to 51.54 euros by 1015 GMT and were the worst performers in the pan-European Stoxx 600 index.
Osram, which had agreed a reorganisation of its German sites last July with trade unions, promising more German jobs in the long term, said it would now enter into additional talks with labour representatives over steps that could cost it 60 to 70 million euros in extraordinary charges.
"The aim is to provide an orderly reorganisation of the German sites and the company's indirect functions which should help secure competitiveness and profitability in the long term," it said in a statement.
Commerzbank analyst Sebastian Growe said he expected that capacity adjustments in Germany could lead to Osram cutting hundreds of jobs, or 2 to 3 percent of its global workforce of nearly 27,000.
Osram also cut its guidance for full-year earnings per share to 1.90-2.10 euros from 2.40-2.70 euros.
In the first half, revenues from continuing operations edged up 1.8 percent to 1.01 billion euros on a comparable basis in its fiscal second quarter through March, but Osram's adjusted EBITDA margin shrank to 15.1 from 17.4 percent.
"Slowing production rates and the rapid decline of legacy technologies such as Xenon are taking their toll and H2 car production will be weaker than Osram expected, particularly in Asia," Jefferies analysts said.
Osram relies on the automotive sector for roughly half of its sales, which means any slowdown in car production weighs on its revenues.
Osram is due to publish full quarterly results on May 3. ($1 = 0.8182 euros) (Reporting by Ludwig Burger and Maria Sheahan Editing by Georgina Prodhan/Keith Weir)